Prefusion rsv f proteins and their use

ABSTRACT

Disclosed are Respiratory Syncytial Virus (RSV) antigens including a recombinant RSV F protein stabilized in a prefusion conformation. Also disclosed are nucleic acids encoding the antigens and methods of producing the antigens. Methods for generating an immune response in a subject are also disclosed. In some embodiments, the method is a method for treating or preventing a RSV infection in a subject by administering a therapeutically effective amount of the antigen to the subject.

RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 17/478,533, filedSep. 17, 2021, which is a continuation of U.S. application Ser. No.16/025,858, filed Jul. 2, 2018, which issued as U.S. Pat. No. 11,130,785on Sep. 28, 2021, which is a continuation of U.S. application Ser. No.14/776,651, filed Sep. 14, 2015, which issued as U.S. Pat. No.10,017,543 on Jul. 10, 2018, which is the U.S. National Stage ofInternational Application No. PCT/US2014/026714, filed Mar. 13, 2014,which was published in English under PCT Article 21(2), which in turnclaims the benefit of U.S. Provisional Application No. 61/780,910, filedMar. 13, 2013, U.S. Provisional Application No. 61/798,389, filed Mar.15, 2013, U.S. Provisional Application No. 61/857,613, filed Jul. 23,2013, and U.S. Provisional Application No. 61/863,909, filed Aug. 9,2013. Each of the prior applications is incorporated by reference hereinin its entirety.

SEQUENCE LISTING

The nucleic and amino acid sequences listed in the accompanying sequencelisting are shown using standard letter abbreviations for nucleotidebases, and three letter code for amino acids, as defined in 37 C.F.R.1.822. Only one strand of each nucleic acid sequence is shown, but thecomplementary strand is understood as included by any reference to thedisplayed strand. The Sequence Listing is submitted as an XML file inthe form of the file named “4239-90594-30_Sequence.xml” (2,527,232bytes), which was created on Sep. 10, 2023, and is incorporated byreference herein.

FIELD

This disclosure relates to polypeptides, polynucleotides, compositions,and methods of their use, for elicitation and detection of an immuneresponse to respiratory syncytial virus (RSV).

BACKGROUND

Respiratory syncytial virus (RSV) is an enveloped non-segmentednegative-strand RNA virus in the family Paramyxoviridae, genusPneumovirus. It is the most common cause of bronchiolitis and pneumoniaamong children in their first year of life. RSV also causes repeatedinfections including severe lower respiratory tract disease, which mayoccur at any age, especially among the elderly or those with compromisedcardiac, pulmonary, or immune systems. Passive immunization currently isused to prevent severe illness caused by RSV infection, especially ininfants with prematurity, bronchopulmonary dysplasia, or congenitalheart disease. Current treatment includes administration of aRSV-neutralizing antibody, Palivizumab (SYNAGIS®; MedImmune, Inc.),which binds a 24-amino acid, linear, conformational epitope on the RSVFusion (F) protein.

In nature, the RSV F protein is initially expressed as a singlepolypeptide precursor, designated F₀. F₀ trimerizes in the endoplasmicreticulum and is processed by a cellular furin-like protease at twoconserved sites, generating, F₁, F₂ and Pep27 polypeptides. The Pep27polypeptide is excised and does not form part of the mature F protein.The F₂ polypeptide originates from the N-terminal portion of the F₀precursor and links to the F₁ polypeptide via two disulfide bonds. TheF₁ polypeptide originates from the C-terminal portion of the F₀precursor and anchors the mature F protein in the membrane via atransmembrane domain, which is linked to an ˜24 amino acid cytoplasmictail. Three protomers of the F₂-F₁ heterodimer assemble to form a matureF protein, which adopts a metastable prefusion conformation that istriggered to undergo a conformational change that fuses the viral andtarget-cell membranes. Due to its obligatory role in RSV entry, the RSVF protein is the target of neutralizing antibodies and the subject ofvaccine development; however, like other RSV antigens, prior efforts todevelop an RSV F protein-based vaccine have proven unsuccessful.

SUMMARY

As described herein, the three-dimensional structure of RSV F protein inits pre-fusion conformation was elucidated. The disclosure reveals forthe first time the atomic level details of the prefusion conformation ofRSV F, which presents a unique antigenic site (“antigenic site Ø”) atits membrane distal apex. Using the three-dimensional structure ofprefusion F as a guide, stabilized forms of prefusion F (“PreF”antigens) were engineered and constructed, and used to generate RSVneutralizing immune responses many fold greater than that achieved withprior RSV F protein-based immunogens, and which provide protectionagainst RSV challenge in animal models. The PreF antigens can be used,for example, as both potential vaccines for RSV and as diagnosticmolecules.

Isolated recombinant RSV F proteins that are stabilized in a prefusionconformation, as well as nucleic acid molecules encoding the recombinantRSV F proteins are disclosed. In several embodiments, the recombinantRSV F proteins are stabilized in a prefusion conformation that canspecifically bind to a prefusion-specific antibody, such as a D25, 5C4,AM22, and/or MPE8 antibody. In several embodiments, the recombinant RSVF protein comprises an antigenic site Ø comprising residues 62-69 and196-209 of a RSV F protein sequence, such as SEQ ID NO: 370. In someembodiments, the immunogen can specifically bind to the antibody afterthe immunogen is incubated at 20° C. in phosphate buffered saline atphysiological pH for at least 24 hours in the absence of the antibody.In further embodiments, the immunogen can form a homogeneous populationwhen dissolved in aqueous solution, wherein at least 90% of theimmunogen in the population can specifically bind to theprefusion-specific antibody.

In some embodiments, the F₂ and F₁ polypeptides comprise RSV F positions62-69 and 196-209, respectively, and the F₂ polypeptide comprise orconsists of 8-84 residues of RSV F positions 26-109, and the F₁polypeptides comprise or consists of 14-393 residues of RSV F positions137-529, wherein the RSV F positions correspond to the amino acidsequence of a reference F₀ polypeptide set forth as SEQ ID NO: 124.

In several embodiments, the recombinant RSV F protein includes one ormore amino acid substitutions that stabilize the protein in theprefusion conformation, for example, that stabilize the membrane distalportion of the F protein (including the N-terminal region of the F1polypeptide) in the prefusion conformation. For example, the amino acidsubstitution can introduce a non-natural disulfide bond or can be acavity-filling amino acid substitution. In several embodiments, therecombinant RSV F protein includes S155C and S290C substitutions thatform a non-natural disulfide bond that stabilizes the protein in aprefusion conformation; that is, in a conformation that specificallybinds to one or more pre-fusion specification antibodies, and/orpresents an antigenic site, such as antigenic site Ø, that is present onthe pre- but not post-fusion conformation of RSV F protein. In furtherembodiments, the recombinant RSV F protein can further include a F, L,W, Y, H, or M substitution at position 190, position 207, or positions190 and 207. In one non-limiting example, the recombinant RSV F proteinincludes S155C, S290C, S190F, and V207L substitutions (referred toherein as “DSCav1”).

In additional embodiments, the recombinant RSV F protein can include oneor more modifications to the C-terminus of the F1 polypeptide (such astruncations and amino acid substitutions) that, together with themodifications that stabilize the membrane distal region of the Fpolypeptide, can increase stabilization of the recombinant F protein inthe prefusion conformation. Exemplary modifications include linkage ofthe F₁ polypeptide to a trimerization domain (such as a foldon domain)or introduction of one or more cysteine residues in the C-terminalregion of the F1 polypeptide (for example, at positions 512 and 513)that can form inter-protomer disulfide bonds.

The PreF antigen can be included on a protein nanoparticle, or on aviral-like particle. Nucleic acid molecules encoding the PreF antigensare also disclosed. In some embodiments, the PreF antigen includes arecombinant RSV F protein that is a single chain RSV F protein.

Additional embodiments include an epitope-scaffold protein including RSVF positions 62-69 and 196-209, or a circular permutant thereof, linkedto a heterologous scaffold protein, wherein the epitope scaffold proteinspecifically binds to a prefusion-specific antibody.

Compositions including the PreF antigens, protein nanoparticle, nucleicacid molecule or vector are also provided. The composition may be apharmaceutical composition suitable for administration to a subject, andmay also be contained in a unit dosage form. The compositions canfurther include an adjuvant.

Methods of generating an immune response in a subject are disclosed, asare methods of treating, inhibiting or preventing a RSV infection in asubject. In some embodiments of the methods, a subject, such as a humanor bovine subject, is administered an effective amount of a disclosedantigen and/or a nucleic acid molecule encoding a disclosed antigen. Insome embodiments, the methods include administration of an immunogeniccomposition including an adjuvant selected to elicit a Th1 biased immuneresponse in a subject. In additional embodiments, the methods include aprime boost immunization, using human subtype A and human subtype B RSVF proteins stabilized in a prefusion conformation with the modificationsdisclosed herein. Methods for detecting or isolating an RSV bindingantibody in a subject infected with RSV are disclosed. In someembodiments, the recombinant RSV F proteins can be used to detect andquantify target antibodies in a polyclonal serum response.

The foregoing and other objects, features, and advantages of theembodiments will become more apparent from the following detaileddescription, which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A-1C are a set of graphs and an diagram illustrating RSVneutralization, F glycoprotein recognition, and the crystal structure ofhuman antibody D25 in complex with the prefusion RSV F trimer. Theprefusion conformation of RSV F is metastable, and when expressed in asoluble form readily adopts the postfusion state; a number of potentantibodies, including D25, bind to a newly revealed antigenic site atthe top of the prefusion F glycoprotein. (A) RSV neutralization byantibodies including palivizumab, the FDA-approved prophylactic antibodyto prevent severe RSV disease. (B) Enzyme linked immunosorbant assay(ELISA) measuring antibody binding to postfusion F glycoprotein. (C)D25-RSV F trimer structure in ribbon and molecular surfacerepresentations. One protomer of the F glycoprotein trimer is shown asribbons. Molecular surfaces are shown for the other two F protomers. TheD25 Fab bound to the F protomer shown in ribbons is also displayed inribbon representation, with heavy chain shaded dark grey and light chainshaded light grey. The other D25 Fabs are shaded same, but shown insurface representation.

FIGS. 2A and 2B are a set of diagrams and a sequence aligned with RSVsecondary structure illustrating the structural rearrangement of RSV F.To mediate virus-cell entry, the RSV F glycoprotein transitions from ametastable prefusion conformation to a stable postfusion conformation.(A) Prefusion and postfusion structures. Outer images display prefusion(left) and postfusion (right) trimeric structures, shaded the same as inFIG. 1C. A complex glycan, shown as sticks, is modeled at each of thethree N-linked glycosylation sites found in the mature protein. Innerimages display a single RSV F protomer in ribbon representation. (B) RSVF sequence and secondary structure. Sites of N-linked glycosylation arehighlighted by black triangles, antigenic sites are labeled, anddownward arrows indicate the position of furin cleavage sites. Secondarystructures are shown below the sequence (SEQ ID NO: 370), with cylindersrepresenting α-helices and arrows representing β-strands. Disordered ormissing residues are indicated by an “X”; residues that move over 5 Åbetween prefusion and postfusion conformations shown with grey shadowand are boxed.

FIGS. 3A-3C show a set of diagrams and a sequence alignment illustratingthe RSV F interface with D25. Antibody D25 binds a quaternary epitopespanning two protomers at the apex of the prefusion F trimer. (A)Close-up of the interface between D25 and RSV F. Side chains of Fresidues interacting with D25 are labeled and shown as sticks. Oxygenatoms are shaded light grey and nitrogen atoms are shaded dark grey.Hydrogen bonds are depicted as dotted lines. The two images are relatedby a 900 rotation about the vertical axis. (B) Position and conformationof the D25 epitope on the prefusion and postfusion F molecules. RSV Fresidues at the D25 interface are shown. Polarity of α4 and α5_(post)indicated with arrows, with fragment N- and C-termini indicated. (C)Sequence conservation of F residues in regions recognized by D25.Residues 63-74 and 200-213 of SEQ ID NO: 1 (hRSV/A), SEQ ID NO: 129(hRSV/B), and SEQ ID NO: 178, bRSV) are shown. Amino acids in human RSVsubtype B (hRSV/B) or in bovine RSV (bRSV) that differ from hRSV/A areunderlined. Ectodomain is defined as F residues 26-109 and 137-524.

FIGS. 4A-4D are series of graphs and digital images concerning antigenicsite Ø. Highly effective RSV-neutralizing antibodies target a site atthe membrane-distal apex of the prefusion F trimer. (A) The ability ofantibodies to block D25 binding to RSV-infected cells was measured as afunction of antibody concentration. (B) Analysis of RSV F/Fab complexesby negative stain electron microscopy: (Left) Reprojection of a 12 Åslice through the crystal structure of RSV F+D25 Fab filtered to 10 Åresolution and sliced to include the F-trimer cavity. (Middle) Alignedaverage of 263 particles of RSV F+D25 Fab. (Right) Aligned average of550 particles of RSV F+AM22 Fab. Scale bar in middle panel is 50 Å. (C)Fusion inhibition and (D) attachment inhibition activity for antibodiestargeting antigenic site Ø and F-specific antibodies targeting otherantigenic sites. For the attachment-inhibition assay, heparin was usedas a positive control.

FIG. 5 shows a schematic diagram illustrating the methods used toexpress complexes of RSV F and D25. Plasmids expressing RSV F(+) Fd (Fcircle), the D25 light chain (L circle), and the D25 heavy chain (withor without a stop codon in the hinge region, H circle) weresimultaneously transfected into HEK293 cells in suspension.Alternatively, the RSV F(+) Fd plasmid could be transfected, withpurified D25 Fab or IgG added to the cells 3 hours post-transfection.The best yields were obtained by simultaneously expressing F and D25 Fab(˜1.0 mg of purified complex per liter of cells).

FIG. 6 shows a set of ribbon diagrams illustrating the comparison ofD25-bound RSV F to prefusion PIV5 F. Ribbon representation of D25-boundRSV F (+) Fd (left) and PIV5 F-GCNt (right). There is excellentagreement of secondary structure elements between the two proteins,despite having only ˜12% sequence identity. One of the most strikingdifferences is the location of the fusion peptide (N-terminus of F₁subunit), also shown in FIG. 7 . The PIV5 F structure was described asconsisting of three domains: I, II and III (Yin et al., Nature, 439, 38(2006)). Domain III termed the membrane distal lobe, whereas domains Iand II encompass the central barrel and membrane proximal lobe. Thecleaved PIV5 structure shown here was generated from PDB ID: 4GIP (Welchet al., Proc. Natl. Acad. Sci., U.S.A. 109, 16672 (2012)).

FIG. 7 shows a series of diagrams illustrating Type I prefusion viralglycoproteins. Prefusion structures of RSV F, PIV5 F (PDB ID: 4GIP(Welch et al., Proc. Natl. Acad. Sci., U.S.A. 109, 16672 (2012)),influenza HA (PDB ID: 2HMG; Wilson et al., Nature, 289, 366 (1981)) andEbola GP (PDB ID: 3CSY; Lee et al., Nature, 454, 177 (2008)) are shownas molecular surfaces, with each protomer colored differently. On thebottom row, a sphere is shown for the C-terminal residue of F₂ (RSV andPIV5) or HA₁(Flu), and a sphere is show for the N-terminal residue ofthe fusion peptide. The RSV and PIV5 are both paramyxoviruses and theirF proteins share ˜12% sequence identity. Although Ebola GP is a type Ifusion protein, it lacks a free N-terminal fusion peptide on GP2, andinstead contains an internal fusion loop that is commonly seen in typeII and type III fusion proteins. Thus, the Ebola GP was omitted from thefusion peptide comparison.

FIG. 8 is a set of graphs concerning RSV neutralization by IgG and Fab.D25, AM22 and Motavizumab neutralize RSV equally well as IgG or Fab.Note that the x-axis for the Motavizumab plot is different than theothers.

FIGS. 9A and 9B are a series of diagrams and graphs illustratingproperties of antigenic sites on the RSV F glycoprotein. Only antibodiesdirected to antigenic site Ø bind specifically to the prefusionconformation and have exceptional neutralization potency. (A) For siteØ, an image of a single D25 Fab binding to the prefusion RSV F trimer isshown, along with neutralization curves for AM22 and D25. For site I,arrows point to Pro389, a known escape mutation (Lopez et al., J.Virol., 72, 6922 (1998)). A neutralization curve is shown for antibody131-2a. Like antibody 2F (Magro et al., J. Virol., 84, 7970 (2010)),antibody 131-2a only neutralizes ˜50% of the virus. (B) For antigenicsites II and IV, models of Motavizumab (site II) and 101F (site IV)binding to the prefusion and postfusion (McLellan et al., J. Virol., 85,7788 (2011)) F structures were made using the coordinates ofantibody-peptide structures (McLellan et al., J. Virol., 84, 12236(2010); McLellan et al., Nat. Struct. Mol. Biol., 17, 248 (2010)).

FIG. 10 shows an image of a polyacrylamide gel illustrating expressionof the recombinant RSV F protein construct with S155C and S290C aminoacid substitutions and a Foldon domain linked to the C-terminus of F₁,and a set of diagrams illustrating that the disulfide bond between S155Cand S290C can only form in the prefusion conformation of RSV F protein.

FIG. 11 is a set of graphs showing results from ELISA and gel filtrationassays using the recombinant RSV F protein construct with S155C andS290C amino acid substitutions and a Foldon domain linked to theC-terminus of F₁. The ELISA data indicate that the S155C/S290C constructis specifically bound by RSV F prefusion specific antibodies. The gelfiltration profiles show that the S155C/S290C construct exists solely asa trimer, whereas aggregates and rosettes form in solution with acontrol RSV F construct lacking the S155C/S290C substitutions.

FIG. 12 shows negative-stain electron microscopy images of recombinantRSV F protein construct with S155C and S290C amino acid substitutionsand a Foldon domain linked to the C-terminus of F1. The images below thelarge panel are 2D averages of individual particles. The resultsindicate that the S155C/S290C construct is stabilized in the prefusionconformation.

FIGS. 13-14 show a set of graphs illustrating the neutralizing antibodyresponse of mice administered native RSV (RSV), formalin inactivated RSV(FI-RSV), the recombinant RSV F protein construct with S155C and S290Camino acid substitutions and a Foldon domain linked to the C-terminus ofF₁ (prefusion F), or a RSV F protein construct stabilized in thepostfusion conformation (postfusion RSV). The antibody response at 5weeks (FIG. 13 ) and 7 weeks (FIG. 14 ) post-initial immunization isshown.

FIG. 15 shows digital images of the crystals of a soluble recombinantRSV F protein stabilized in a prefusion conformation by S155C and S290Csubstitutions. Left, standard light images; Right, ultraviolet images,indicative of proteins. The formation of crystals from aqueous bufferedsolutions demonstrates that this protein is substantially homogeneous insolution.

FIG. 16 shows the design of a RSV F protein based antigen (RSV_AF(+)FdTHS) stabilized by engineered disulfide bond mutations S155C andS290C (“DS”), cavity-filling mutations S190F and V207L (“Cav1”), andappended C-terminal heterologous trimerization domain (Fd). TheD25-bound RSV F structure is shown with two of the protomers displayedas a molecular surface colored pink and tan, and the third protomerdisplayed as ribbons. The N- and C-terminal residues of F₁ that movemore than 5 Å between the pre and postfusion conformations are shown.Insets show the engineered disulfide bond between residues S155C andS290C (named “DS”), as well as the space-filling cavity mutations S190Fand V207L (named “Cav1”). A model of the T4 phage fibritin trimerizationdomain is shown at the base of the prefusion trimer. The RSV F proteinincluding the S155C and S290C, and S190F and V207L substitutions inhuman RSV subtype A, and the appended C-terminal heterologous Foldondomain, is termed RSV_A F(+)FdTHS DSCav1. Mutations compatible with D25recognition, but insufficiently stable to allow purification as ahomogenous trimer, are labeled and shown in black stick representation.

FIG. 17 shows the antigenic characterization of RSV_A F(+)FdTHS DSCav1.The association and dissociation rates of soluble D25, AM22, 5C4, 101F,Motavizumab, and Palivizumab Fab interaction with immobilized RSV_AF(+)FdTHS DSCav1 were measured using an OctetRED 384™ instrument(ForteBio, Melno Park, CA). Equilibrium dissociation constants for eachantibody are provided.

FIG. 18 shows size exclusion chromatography of RSV_A F(+)FdTHS DSCav1.Purified protein, after thrombin cleavage to remove the tags, was passedover a 16/70 Superose 6 size exclusion column. The elution volume isconsistent with a glycosylated trimer.

FIG. 19 shows a table listing antigenic and physical characteristics ofRSV_A F(+)FdTHS variants stabilized by DS, Cav1 or DSCav1 alterations.The left most column defines the RSV F variant, and the rest of thecolumns provide variant properties, including yield from transientlyexpressed plasmids, antigenicity against various antigenic sites, andthe retention of D25-binding (provided as a fractional amount) after 1hour of incubation at various temperatures, pHs, and osmolality, or to10 cycles of freeze-thaw. The DSCav1 variant retains antigenic site Ørecognition, with improved physical stability, as judged by higherretention of D25-reactivity after exposure to extremes of temperature,pH, osmolality and freeze-thaw, then either DS or Cav1 variants.

FIG. 20 shows a ribbon representation of the 3.1 Å crystal structure ofRSV_A F(+)FdTHS DSCav1. Thicker ribbons correspond to increasingB-factors. Despite stabilizing mutations, antigenic site Ø, at thetrimer apex, retains significant flexibility.

FIG. 21 shows comparison of RSV_A F(+)FdTHS DSCav1 to D25-bound RSV F.Ribbon representation of RSV_A F(+)FdTHS DSCav1, superposed with aribbon representation of D25-bound RSV F colored white (PDB ID 4JHW).The images are related by a 90° rotation about the vertical axis.

FIG. 22 shows stabilizing mutations in RSV_A F(+)FdTHS DSCav1 structure.Ball-and-stick representation of RSV_A F(+)FdTHS DSCav1 crystalstructure with 2F₀-F_(c) electron density contoured at 1a is shown as amesh. These images indicate that electron density corresponding to thedisulfide bond between cysteine residues 155 and 290 (left), as well asthe cavity-filling Phe190 residue (right), is observed.

FIG. 23 shows mouse immunogenicity of RSV_A F(+)FdTHS DSCav1. Ten CB6mice per group were immunized with 10 μg of RSV_A F(+)FdTHS DSCav1protein mixed with 50 μg of poly I:C adjuvant. Immunizations occurred at0 and 3 weeks, and sera from week 5 and week 7 were tested forneutralization of RSV subtype A (RSV_A) and B (RSV_B). Mean values areindicated by horizontal lines.

FIG. 24 shows non-human primate (NHP) immunogenicity of RSV_A F(+)FdTHSDSCav1. Four RSV-naïve rhesus macaques per group were immunized with 50μg of RSV_A F(+)FdTHS DSCav1 protein mixed with 500 μg of poly I:Cadjuvant. Immunizations occurred at 0 and 4 weeks, and sera from week 6were tested for neutralization of RSV subtype A (left) and B (right).Mean values are indicated by horizontal lines.

FIGS. 25A-25C show plasmid maps of expression vectors. (A) A map of theRSV_A F(+)FdTHS DSCav1 paH expression vector (SEQ ID NO: 384) forexpressing recombinant RSV F protein from human subtype A includingS155C, S290C, S190F and V207L amino acid substitutions, fused to aC-terminal Foldon domain, thrombin cleavage site, 6×His tag and aStrepTag II. (B) A map of the RSV_B (B1) F(+)FdTHS DSCav1 paH expressionvector (SEQ ID NO: 386) for expressing recombinant RSV F protein fromhuman subtype B (strain B1) including S155C, S290C, S190F and V207Lamino acid substitutions, fused to a C-terminal Foldon domain, thrombincleavage site, 6×His tag and a StrepTag II. (C) A map of the RSV_B(18537) F(+)FdTHS DSCav1 paH expression vector (SEQ ID NO: 388) forexpressing recombinant RSV F protein from human subtype B (strain 18537)including S155C, S290C, S190F and V207L amino acid substitutions, fusedto a C-terminal Foldon domain, thrombin cleavage site, 6×His tag and aStrepTag II.

FIGS. 26A-26D illustrate structure-based vaccine design for RSV: asupersite paradigm. (A) Natural infection by RSV elicits diverseantibodies, with a range of viral neutralization potencies. (B) Acluster of epitopes for naturally elicited, highly potent antibodiesdefines a supersite of viral vulnerability. Shown are antigen-bindingfragments of the potently neutralizing antibody D25 recognizing anepitope at the apex of the RSV F trimer. Spatially overlapping epitopesat the trimer apex are also recognized by the AM22 and 5C4 antibodies,which share the same desired neutralization characteristics as D25.These overlapping epitopes define antigenic site Ø as a supersite of RSVvulnerability. (C) After selection of a target supersite, an iterativeprocess of design, characterization of antigenic and physicalproperties, atomic-level structure determination, and assessment ofimmunogenicity allows for the structure-based optimization of vaccineantigens encoding the target supersite. (D) Because the supersite ofviral vulnerability naturally elicits highly protective antibodies,immunization with “supersite immunogens” more easily elicits protectiveresponse than immunogens based on viral regions recognized bysubdominant or non-potently neutralizing antibodies.

FIG. 27 shows design of soluble trimeric site Ø-stabilized RSV Fs. Over100 variants of RSV F containing the T4 fibritin-trimerization domain(foldon) were designed to more stably retain antigenic site Ø. Shownhere is the structure of the RSV F trimer in its D25-bound conformationwith modeled foldon. The trimer is displayed with two protomers asmolecular surfaces shaded light grey tan and pink, and the thirdpromoter as ribbons. The ribbon is shaded white in regions where it isrelatively fixed between pre- and postfusion, while the N- andC-terminal residues that move more than 5 Å between pre- and postfusionconformations are shaded darker grey. Mutations compatible withexpression and initial D25 recognition, but insufficiently stable toallow purification as a homogenous trimer are labeled and shown in blackstick representation. Insets show close-ups of stabilizing mutations instick representation for DS, Cav1 and TriC variants, all of which stablyretain antigenic site Ø (FIG. 31 ).

FIGS. 28A-28C show structures of RSV F trimers, engineered to preserveantigenic site Ø. (A-C) Six structures for RSV F variants are shown,labeled by stabilizing mutation (DS, Cav1, DS-Cav1, and DS-Cav1-TriC)and by the lattice (cubic and tetragonal) and crystallization pH. (A)RSV F trimers are displayed in Cα-worm representation, colored accordingto atomic mobility factor. Missing regions are shown as dotted lines.These occur at the C-terminal membrane-proximal region, where the foldonmotif is not seen, except in the DS-Cav1-TriC structure (far right). Inthe DS structure, two loops in the head region are also disordered. (B)Antigenic site Ø of a RSV F protomer is displayed in ribbon diagram,with the structure of D25-bound RSV F in gray and different variantsindicated. Stabilizing mutations are labeled and shown in stickrepresentation. (C) Atomic-level details are shown in stickrepresentation, with regions of RSV F that change conformation betweenprefusion and postfusion conformation in dark grey, and those thatremain constant in lighter gray. Stabilizing carbon atoms forstabilizing mutations are indicated. In Cav1 (pH5.5) and in DS-Cav1(pH5.5) novel features were observed involving the interaction of theC-terminus of the F₂ peptide with a sulfate ion and the fusion peptide.In the DS-Cav1-TriC structure, the D486H-E487Q-F488W-D489H mutationsinteract with the two neighboring protomers around the trimer axis.

FIGS. 29A-29B show results concerning immunogenicity of engineered RSV Ftrimers. RSV F proteins engineered to stably display antigenic site Øelicit neutralizing titers significantly higher than those elicited bypostfusion F. (A) Neutralization titers of sera from mice immunized with10 μg of RSV F (left). Postfusion F, as well as RSV F bound byantibodies AM22 or D25, were immunized at 20 μg per mouse (right).Geometric mean is indicated by a horizontal line. (B) Neutralizationtiters of sera from rhesus macaques immunized with 50 μg of RSV Fprotein variants. Geometric mean is indicated by a horizontal line.Protective threshold is indicated by a dotted line, and p-value providedfor postfusion versus DS-Cav1.

FIGS. 30A-30D show how physical, structural, and antigenic properties ofantigenic site Ø-stabilized RSV F correlate with immunogenicity. (A)Physical stability of site Ø versus immunogenicity. Inset showsinformation transFer Physical stability as determined by 7 measurementsof D25 retention of activity in FIG. 31 were averaged (horizontal axis)and compared to elicited RSV-protective titers from FIG. 29 (verticalaxis). (B) Structural mimicry of site Ø versus immunogenicity. Insetshows information transfer. Structural mimicry (horizontal axis) is thermsd between different structures (FIG. 28 ) and D25-bound RSV F for allatoms within 10 Å of D25. This is compare to elicited RSV-protectivetiters from FIG. 29 (vertical axis). (C) Antigenic analysis of sera fromimmunized macaques. Binding of sera to immobilized DS-Cav1 (left) orpostfusion F (right) was measured directly (Blank, black bars) or afterincubation with excess postfusion F (dark grey bars) or DS-Cav1 (lightgrey bars). The mean response of the four macaque sera is graphed, witherror bars for the standard deviation. (D) Correlation of immunogenicityand antigenicity of NHP sera. The mean neutralization titers of the fourmacaque sera in each group are plotted against the ratio of bindingresponses to DS-Cav1 and postfusion F.

FIGS. 31A-31B are a table showing the results of antigenic and physicalcharacterization of RSV F protein immunogens. ^(#)Defined for trimericstate, but if no trimeric state could be purified, then the oligomericstate of the dominant oligomeric species. If total yield is <0.1 mg/l,then oligomeric state is not determined (N.D.). *Yield is shown forspecific oligomeric state. >1000 nM=no binding at 1 μM Fabconcentration. N/A=not applicable.

FIG. 32 shows the location of S155 and S290 in the pre- and postfusionRSV F structures. The β-carbons of serine residues 155 and 290 are 4.4 Åapart in the D25-bound RSV F structure and 124.2 Å apart in thepostfusion structure. The mutations S155C and S290C (called “DS”)restrained the structure in the prefusion conformation.

FIGS. 33A-33C shows negative staining of stabilized F-protein. A) and B)show representative fields of negatively stained specimens for DS andDS-Cav1. The proteins are highly homogenous with <1% and <0.1% of post-Fconformations observed in DS and DSCav1, respectively. Examples ofpost-F conformations are indicated by black arrows. Bar=50 nm. 2Dparticle averages are shown as insets in the top right corner at twicethe magnification. Bar=5 nm. C) shows a comparison of the 2D averageswith the average of F+D25 complex (McLellan et al. 2013). Bar=5 nm.

FIG. 34 shows the antibody D25 based ELISA of the crude culturesupernatants is correlated (Spearman R=0.7752 and a P value=0.0041) tothe yield of purified oligomeric RSV F glycoprotein variants. RSV Fglycoprotein production by 293 Expi cells was determined by D25 ELISA ofthe crude culture supernatants at 4° C. one week after harvesting andfound to correlate with the yield of pure oligomeric RSV F glycoproteinvariants.

FIG. 35 shows the antibody motavizumab based ELISA of the crude culturesupernatants versus the yield of purified RSV F glycoprotein variants.(A) RSV F glycoprotein production by 293 Expi cells was determined bymotavizumab ELISA of the crude culture supernatants at 4° C. immediatelyupon harvest and (B) one week after harvesting. ELISA data is plottedversus the yield of RSV F glycoprotein variants after streptactinaffinity. Interestingly, three proteins, RSV F(+) Fd and two variantsF137W-F140W and T357C-N371C were detected as high expressers bymotavizumab ELISA but low yields were obtained after large scalepurification (points shown along the ordinate).

FIG. 36 shows the characterization of engineered RSV F glycoproteinsusing size exclusion chromatography. RSV F variants, a: Cav1; b:Cav1-TriC; c: DS-Cav1-TriC; d: F488W; e: DS-Cav1; f: TriC, g: DS-TriC;h: DS; exhibit elution profiles characteristic of a globular trimericprotein, whereas RSV F variants i: S190F-V296F; j: K87F-V90L; k:V207L-V220L; 1: V178N; m: S403C-T420C; n: I506K; o: V185E; p:F137W-F140W-F488W; q: D486H-E487Q-D489H exhibit elution profilescharacteristic of higher oligomeric species. Protein standards of knownmolecular weight are labeled on the base of the chromatogram.

FIG. 37 shows antigenic site Ø shown from above. The regions of DS whichare not visible are represented by dotted lines.

FIGS. 38A-38B shows results concerning antigenic characterization ofimmunogen-adjuvant complexes for non-human primate immunization. (A) RSVF post fusion, DS and DS-Cav1sample reactivity was assessed against 1 μMD25 antigen-binding fragment less than 3 h following immunogenformulation with Poly J:C and NHP immunizations at day 0 and (B) week 4.

FIGS. 39A-39B shows antigenic analysis of sera from immunized mice andrhesus macaques. A) Sera from mice immunized with multiple stabilizedRSV F variants was assessed for binding to immobilized DS-Cav1 wasmeasured directly or DS-Cav1 after incubation with excess D25 ormotavizumab antigen-binding fragments to assess the site Ø or site IIresponses. B) Sera from rhesus macaques was assessed for binding toimmobilized DS-Cav1 or postfusion RSV F variants also blocked with D25or motavizumab antigen-binding fragments. The mean response of theanimal sera is shown, with error bars for the standard deviation.

FIG. 40 shows crystallographic data collection and refinementstatistics.

FIG. 41 shows the effect of using RSV subtype B constructs with the DSsubstitutions and that adjuvants including TLR4 agonists can work withthe stabilized F protein. CB6F1/J mice were immunized with 10 μg of theDS S155C/S290C version of stabilized prefusion F formulated with 50 μlof Ribi (Ribi adjuvant system, Sigma). Mice were inoculated at 0 and 3weeks with either the subtype A construct (SEQ ID NO: 185), the subtypeB construct (SEQ ID NO: 1479), or both (10 μg of each). At the 5 weektime point (2 weeks after the second injection), serum was obtained forneutralization assays. The two major findings from this experiment werethat, 1) preF_(A)-DS and preF_(B)-DS induce equal levels of neutralizingactivity against RSV subtype A, while preF_(B)-DS induced a higher levelof neutralizing activity than preF_(B)-DS against RSV subtype B. Thissuggests that using the RSV subtype B constructs may have bettercross-neutralizing potential than subtype A constructs or that hybridversions of RSV F that include elements from both subtypes may bepreferred. 2) The Ribi adjuvant is an oil-in-water emulsion containingmonophosphoryl lipid A, which is a TLR4 agonist and representative ofsome of commercial adjuvants. These data show that in addition topolyL:C (a TLR3 agonist), adjuvants that include TLR4 agonists functionwith the stabilized prefusion F protein as a vaccine antigen.

FIG. 42 shows that the stabilized prefusion F can be formulated in alumas well as polyL:C and retain immunogenicity conferred by antibodyresponses to antigenic site Ø. BALB/c mice were immunized with 20 μg ofthe DS S155C/S290C version of stabilized prefusion F derived fromsubtype A and formulated with alum (aluminum hydroxide gel 10 mg/ml,Brenntag, Frederikssund, Denmark) or polyL:C. Mice were inoculated at 0and 3 weeks, and at the 5 week time point (2 weeks after the secondinjection), serum was obtained for neutralization assays.

FIG. 43 is a schematic diagram illustrating an exemplary design schemefor prefusion-stabilized single-chain RSV F (scF) antigens, includingthe variables that are involved with several different RSV scF designs.Design elements that pertain to RSV scF no. 9 (BZGJ9 DS-Cav1; SEQ ID NO:669 are outlined in dark grey.

FIGS. 44A and 44B illustrate the design of single-chain RSV F constructno. 9 (scF no. 9; BZGJ9 DSCav1; SEQ ID NO: 669). Numbering indicatesresidue locations of the various components described below. (A)Schematic representations of furin-cleaved RSV F(+) glycoprotein asshown in FIG. 44B (top), and RSV scF no. 9 design (bottom), showing thefoldon trimerization domain (grey oval), and the artificial linker (greysquare) bridging the polypeptide backbones of F₂ (left) and F₁ (right).(B) Structural basis for RSV scF no. 9 design using aprefusion-stabilized RSV F(+) structure as a model (PBD ID: 4MMV,incorporated by reference herein in its entirety). RSV F(+) is shown incartoon representation and the foldon trimerization domain shown insphere representation. Shown on the left is the prefusion-stabilized RSVF(+) trimer, with the three protomers colored black, gray, and white.Shown on the right is a single RSV F(+) protomer showing F₁ (mediumgray), F₂ (dark grey), the fusion peptide (indicated), and the foldontrimerization domain (light grey, indicated). The inset shows the fusionpeptide in stick representation, and the location of the flexible linkersequence (dashed line) joining residues 104 and 147.

FIG. 45 shows a table concerning the design, oligomeric state, andproduction yield of engineered single-chain RSV F constructs expressedin HEK293-F cells. RSV F construct no. 9 DSCav1 (scF no. 9; BZGJ9DSCav1; SEQ ID NO: 669), RSV F construct no. 10 DSCav1 (scF no. 10;BZGJ10 DSCav1; SEQ ID NO: 670) RSV F construct no. 11 DSCav1 (scF no.11; BZGJ11 DSCav1; SEQ ID NO: 671) are indicated. The provided linkersequences include GSGNIGLGG (SEQ ID NO: 364), GSGGNGIGLGG (SEQ ID NO:359), GSGNVLGG (SEQ ID NO: 361), and GSGNVGLGG (SEQ ID NO: 362). (%)Prefusion stabilizing mutations include the following: S155C and S290C(DS); S190F and V207L (Cav1); no additional mutations (a). All variantscontain the point mutation L373R. (==) Trimerization domains include thefollowing: L512C and L513C (CC); D486C, E487P, and F489C (CPC). (#)Variants were often observed to exist in a mixture of oligomer states onsize chromatography. If a measureable trimeric fraction was observed,then then oligomeric state is listed as “Trimer”. If no trimericfraction was observed, then the oligomeric state of the dominant speciesis provided. If the total yield prior to size chromatography was <0.1mg/L, then oligomeric state is listed as not determined (N.D.). Ifoligomeric state was indistinguishable by size exclusion chromatography,oligomeric state is listed as “Aggregate”. (*) Yield shown wascalculated post-StrepTag purification and is listed for the specifiedoligomeric state. (Φ) HEK 293F yield is estimated based on observedratio between Expi293F expression yield and Freestyle293F expressionyield seen in scF constructs (˜2:1).

FIGS. 46A and 46B are a set of graphs illustrating characterization ofthe engineered single-chain RSV F glycoproteins by size-exclusionchromatography. (A) Size-exclusion profiles of RSV scF variants (scF no.3, 4, 6, 8 though 11) and RSV F(±) containing DS-Cav1 stabilizingmutations. Single-chain constructs were expressed in HEK293F cells andF(+) DS-Cav1 was expressed in Expi 293-F cells. F(+) DS-Cav1 and scF no.3 DS-Cav1, no. 4 DS-Cav1, no. 6 DS-Cav1, and no. 9 DS-Cav1 exhibitelution profiles characteristic of a globular trimeric protein, whereasscF no. 11 DSCav1 exhibits an elution profile characteristic of aglobular monomeric protein. RSV scF no. 8 DS-Cav1 and scF no. 10 DS-Cav1exhibit elution profiles suggesting a heterogeneous mixture of bothmonomeric and trimeric species. (B) Size-exclusion profiles of RSV F(+)DS-Cav1 and RSV scF no. 9 containing different stabilizing mutations.F(+) DS-Cav1, and scF no. 9 Cav1 were expressed in Expi 293-F cells andthe remaining scF no. 9 variants were expressed in HEK293F cells. Theslight deviation in the elution profiles of scF no 9 variants suggestthat scF no. 9 runs at a higher molecular weight than trimeric F(+). Anasterisk indicates that purification tags were cleaved prior to gelfiltration.

FIG. 47 is a table summarizing the results of antigenic characterizationof RSV scF no. 9 DS-Cav1.

FIG. 48 is a table showing the crystallographic data and refinementstatistics for the three dimensional structure of RSV scF no. 9 DS-Cav1.

FIGS. 49A and 49B show a series of diagrams concerning the crystalstructure of RSV scF no. 9 DS-Cav1 trimer. The orientation of theprotomer displayed in cartoon representation (dark grey) is keptconstant. Thick dotted lines represent the C-terminal foldon motiflocated at the membrane-proximal region, which is not visible in thecrystal structure. (A) RSV scF no. 9 DS-Cav1 trimer displayed withprotomers in cartoon representation and ribbon representation (darkgrey), and molecular surface representation (light grey). Inset showsenlargement of the “GS” scF no. 9 linker loop (indicated) and theadjacent protomer (dark grey), both in stick representation. (B)Prefusion stabilizing mutations in the RSV scF no. 9 DS-Cav1 structure.DS and Cav1 prefusion stabilizing mutations are indicated and shown instick representation.

FIG. 50 is a diagram illustrating the structural alignment of RSV scFno. 9 DS-Cav1 (medium grey) with the F(+) DS-Cav1 structure (light gray;rmsd=0.839 Å) and with the D25-bound F(+) structure (dark gray;rmsd=0.534 Å), all displayed in cartoon representation. Inset shows aclose-up of the scF no. 9 linker loop and the fusion peptides of theF(+) DS-Cav1 structure, and the D25-bound F(+) structure.

FIG. 51 shows diagrams illustrating the comparison of RSV scF designsno. 3, 4, 6, 8-11 using the crystal structure of RSV scF no. 9 DS-Cav1.Thick dotted lines represent the C-terminal foldon motif. RSV scF no. 9DS-Cav1 protomer displayed in cartoon representation (dark grey). Insetshows enlargement of the “GS” scF no. 9 linker loop in stickrepresentation joining residues 105 (F₂) and 145 (F₁). The predictedlocations of the flexible linker sequences for scF designs no. 3, 4, 6and 8 (thin dotted line) joining residues 97 (F₂) and 150 (F₁) aremapped onto the scF no. 9 DS-Cav1 crystal structure. The predictedlocations of the linker sequences for scF designs no. 3, 4, 6 and 8(thin dotted lines) are mapped onto the scF no. 9 DS-Cav trimerstructure. Linker end point residue locations are approximated.

FIG. 52 shows a set of digital images concerning characterization of theengineered single-chain RSV F glycoproteins characterized by SDS-PAGEgel electrophoresis post StrepTag purification. RSV scF constructs wereexpressed in HEK293F cells and purified by His₆-tag and StrepTagaffinity chromatography.

FIG. 53 is a set of graphs and a table providing week 5 neutralizationdata for the indicated constructs (10 animals/group). Immunizations atWeek 0 and Week 3 with 10 μg protein+50 μg Poly I:C per animal.

FIG. 54 is a ribbon and stick diagram highlighting the Proline residueat RSV F position 101 in the three-dimensional structure of RSV scF no.9 (SEQ ID NO: 669). The structure indicates that the single chain linkerregion may be improved by removing Proline 101 or shortening/mutatingthe linker residues and adjacent residues.

FIG. 55 is a graph and a sequence alignment illustrating modification ofthe scF no. 9 construct (SEQ ID NO: 669) to generate the BZG J9-1 to BZGJ9-10 constructs. The sequence alignment shows BZG J9-1 to BZG J9-10sequences corresponding to RSV F residues 97-159 of SEQ ID NOs: 698-707,respectively. These constructs were expressed in Expi cells and assessedby gel filtration (left).

FIG. 56 is a series of graphs and schematic diagrams illustrating aferritin nanoparticle including the scF no. 9 protein, which wasgenerated by linking the C-terminus of the F1 polypeptide in scF no. 9to a ferritin subunit. This construct is termed“BZGJ9-DS-Cav1-LongLink-Ferritin” and provided as SEQ ID NO: 1429.

FIG. 57 is a set of graphs illustrating the physical stability ofBZGJ9-DS-Cav1-LongLink-Ferritin compared to RSV F DS-Cav1.

FIGS. 58A-58C are a set of graphs and a table illustrating theimmunogenicity of different prefusion stabilized RSV F proteins. Thethree constructs tested were RSV F DSCav1 (SEQ ID NO: 371),BZGJ9-DS-Cav1-LongLink-Ferritin (SEQ ID NO: 1429), and scF no. 9 (alsotermed BZGJ9 DS-Cav1, SEQ ID NO: 669). Macaca mulatta animals of Indianorigin weighing 8.26-11.34 kg were intramuscularly injected withimmunogens at week 0 with 50 μg protein+500 μg Ribi per animal, Boost atWeek 4 with 50 μg protein+500 μg Ribi per animal; immunogenicity wasassessed at week 3.5.

FIGS. 59A and 59B are a set of diagrams illustrating thethree-dimensional structure of the RSV F protein from the B18537 strainwith the DSCav1 mutations (SEQ ID NO: 372) (A) Cartoon representation ofa protomer of RSV F. (B) Trimeric form of the fusion glycoprotein withthe additional protomers shown in surface and ribbon representations.

FIGS. 60A-60D are a set of images illustrating the atomic level detailsof the RSV B18537 F glycoprotein with DSCav1 substitutions, and showingthat the DSCav1 substitutions can be introduced into a RSV Fglycoprotein B subtype to stabilize antigenic site Ø. (A) DS-Cav1mutations are highlighted. (B) Antigenic site Ø located at the apex ofthe trimer is shown in stick representation in dark grey. (C) Theinteraction between the fusion peptide and 3 strands 15, 16 and 19 toform and inter-protomeric elongated sheet. (D) Interaction between theF2 C-terminus and the fusion peptide.

FIGS. 61A and 61B are a set of graphs and digital images illustratingantigenic characterization of RSV B18537 Fusion glycoprotein with DSCav1substitutions. (A) Biolayer Interferometry measurements of prototypicsite-specific antibodies were carried out by serial dilution of each Fabmolecule and the association and dissociation rates to immobilizedB18537 F DSCav1 proteins measured. (B) Structural comparison ofantigenic site Ø from strain B18537 and A2. Surface exposed residuesthat differ between the two strains are labelled.

FIGS. 62A and 62B are graphs illustrating purification of the RSV strainB18537 F protein with DSCav1. A. SDS-PAGE of the elution fraction(reduced and non-reduced) and flowthrough fraction after StrepTagIIaffinity purification. B. Gel filtration of RSV B18537 F glycoprotein inGFB buffer on a 120 ml Superdex-200 size-exclusion column.

FIGS. 63-68 illustrate design and production of trimeric recombinant RSVF proteins stabilized in a prefusion conformation without a C-terminaltrimerization domain to maintain stability of the membrane proximal lobeof RSV F. In place of the C-terminal trimerization domain, a ring ofdisulfide bonds is introduced into the C-terminus of the F1 polypeptideby substituting cysteine residues for amino acids of the (10 helix.

FIGS. 69A-69E are a set of tables showing ELISA data for the indicatedrecombinant RSV F variants. Expression and antigenic stability of RSV Fvariants (SEQ ID NOs: 859-1018). DNA encoding these RSV F variants wastransfect into cell in the 96-well format under conditions where therecombinant RSV F proteins are secreted from the cells into the cellmedia. Each construct contains a leader sequence that causes the proteinto enter the secretory system and be secreted. The medium was thencentrifuged and the supernatant used for antigenicity testing forbinding to the Site Ø specific antibody D25 and the Site II specificantibody Motavizumab (“Mota”, FIGS. 69A-69E). The conditions testedinclude D25 and Mota binding on day 0 (conditions 1 and 2), D25 and Motabinding on day 0 after incubation at 70° C. for one hour (conditions 3and 4), and D25 and Mota binding after 1 week at 4° C. (conditions 5 and6). The control is the DSCav1 construct with a foldon domain. Specificantigenicity data for each construct is provided in FIGS. 69A-69E, withthe conditions tested are noted in the header rows.

FIGS. 70A-70E are a set of schematic diagrams illustrating differentdesign strategies to generate RSV F Antigenic Site Ø Immunogens.Antigenic site Ø includes the D25 recognition site on the outer surfaceof pre-fusion RSV F helix α4 and the loop just N-terminal to helix α1 ofeach protomer. Five methods were used to present isolated Site Øepitopes on the surface of an immunogen: A) circular permutation (i.e.altering secondary structure linkers to alter the connectivity of site Øsegments for reasons of design ease and stability), B) incorporation ofsite Ø into a small scaffold protein, C) trimerization of circularpermutations or scaffolded site Ø to match the native site Øtrimerization observed in the pre-fusion RSV F context (as in the leftpanel), D) including all of domain III for added stability of the site Øfold and E) incorporation of A-D onto a nanoparticle platform for addedimmunogenicity.

FIG. 71 is a summary of the minimal site Ø immunogens that weredesigned, produced and tested for antigenicity to the site Ø specificantibodies D25, AN22 and 5C4 by ELISA under the indicated conditions.The table shows the number of site Ø immunogens that fall within eachdesign category, and which produced an ELISA result of at least 1.5.

FIGS. 72A-72F are a set of tables showing ELISA data for the indicatedminimal site Ø constructs binding to D25, AN22 or 5C4 antibody. Theconditions tested include D25 binding after 0 and 1 week at 4° C.(condition 1) and 2), D25 binding after 1 hr. at 60° C. (condition 3),70° C. (condition 4), 80° C. (condition 5), 90° C. (condition 6), or100° C. (condition 7), AM22 binding after two weeks at 4° C. (condition8), 5C4 binding at week 0 (condition 9). The average of D25, AM22, andD25 binding after 1 hour at 70° C. is also shown (condition 10). ELISAscores of >1.5 are highlighted in dark grey; scores of 0.5-1.5 arehighlighted in light grey.

FIG. 73 is a set of graphs illustrating that immunization with DSversion of stabilized prefusion F subtype A or B or both is inducesneutralizing activity against both subtypes

FIG. 74 is a set of graphs illustrating that DSCav1 antibody response isdurable in mice after two doses with immunization at weeks 0 and 4.

FIG. 75 is a set of graphs illustrating that DS immunization can preventRSV infection in mice.

FIG. 76 is a set of graphs illustrating that DS immunization does notinduce Type 2 cytokine responses in mice post-challenge.

FIG. 77 is a set of graphs illustrating that the neutralizing immuneresponse to DSCav1 is boosted and sustained after a 3^(rd) dose innon-human primates, which have been previously immunized with DS-Cav1 orDS at weeks 0 and 4.

FIG. 78 is a graph illustrating that DS-CAV1 can be effectivelyformulated in alum and retain immunogenicity.

FIG. 79 is a set of graphs illustrating that alum is an effectiveadjuvant for DSCav1 in non-human primates.

FIG. 80 is a graph illustrating that DS-CAV1 is immunogenic whenexpressed from a gene-based vector either alone or as priming for aprotein boost.

FIG. 81 is a set of graphs and a table illustrating that DS-Cav1 RSV FSubtype A or B can boost a prime immunization using gene base deliveryof wildtype F protein in non-human primates.

FIG. 82 is a set of graphs illustrating that DS-Cav1 RSV F Subtype A orB can boosts rAd-F(A)WT-primed non-human primate.

FIG. 83 is a set of graphs illustrating that immunization with the DSversion of stabilized prefusion F subtype A or B or both is inducesneutralizing activity against both subtypes of RSV.

FIG. 84 is a graph illustrating that altering glycosylation reducesimmunogenicity of stabilized prefusion F.

SEQUENCES

In the accompanying Sequence Listing:

-   -   SEQ ID NOs: 1-128 are the amino acid sequences of native RSV F        proteins from RSV type A.    -   SEQ ID NOs: 129-177 are the amino acid sequences of native RSV F        proteins from RSV type B.    -   SEQ ID NOs: 178-184 are the amino acid sequences of native RSV F        proteins from bovine RSV.    -   SEQ ID NOs: 185-350 are the amino acid sequences of recombinant        RSV F proteins.    -   SEQ ID NO: 351 is the amino acid sequence of a T4 fibritin        Foldon domain.    -   SEQ ID NO: 352 and 355-365 are amino acid sequences of peptide        linkers.    -   SEQ ID NO: 353 is the amino acid sequence of a Helicobacter        pylori ferritin protein (GENBANK® Accession No. EJB64322.1,        incorporated by reference herein as present in the database on        Feb. 28, 2013).    -   SEQ ID NO: 354 is the amino acid sequence of an encapsulin        protein (GENBANK® Accession No. YP_001738186.1, incorporated by        reference herein as present in the database on Feb. 28, 2013).    -   SEQ ID NOs: 366 and 367 are the V_(H) and V_(L) amino acid        sequences of the AM22 mAb, respectively.    -   SEQ ID NO: 368 and 369 are the V_(H) and V_(L) amino acid        sequences of the D25 mAb, respectively.    -   SEQ ID NO: 370 is a recombinant RSV F₀ protein variant amino        acid sequence of the prototypical A2 strain (GENBANK accession        No. P03420, incorporated by reference herein as present in the        database on Feb. 28, 2012), including P102A, I379V, and M447V        substitutions compared to the P03420 sequence.    -   SEQ ID NO: 371 is the amino acid sequence of a recombinant RSV F        protein from human subtype A including S155C, S290C, S190F and        V207L amino acid substitutions, fused to a C-terminal Foldon        domain, thrombin cleavage site, 6×His tag and a StrepTag II. The        four mutated residues, and the C-terminal appendage are        underlined.

MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALRTGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLLMOSTPATNNRARRELPRFMNYTLNNAKKTNVTLSKKRKRRFLGFLLGVGSAIASGVAVC K VLHLEGEVNKIKSALLSTNKAVVSLSNGVSVLT F KVLDLKNYIDKQLLPI LNKQSCSISNIETVIEFQQKNNRLLEITREFSVNAGVTTPVSTYMLINSELLSLINDMPITNDQKKLMSNNVQIVROQSYSIM CIIKEEVLAYVVOLPLYGVIDTPCWKLHTSPLCTTNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTMNSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGKTKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKSLYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAIGGYIPEAPRDGQAYVRKDGEWVLLSTELGGLVPRGSHHHHHHSAWSHPQFEK (RSV_A F (+) FdTHS DSCav1)

-   -   SEQ ID NO: 372 is the amino acid sequence of a recombinant RSV F        protein from human subtype B including S155C, S290C, S190F and        V207L amino acid substitutions, fused to a C-terminal Foldon        domain, thrombin cleavage site, 6×His tag and a StrepTag II. The        four mutated residues, and the C-terminal appendage are        underlined.

MELLIHRLSAIFLTLAINALYLTSSQNITEEFYQSTCSAVSRGYFSALRTGWYTSVITIELSNIKETKCNGTDTKVKLIKQELDKYKNAVTELQLLMONTPAANNRARREAPQYMNYTINTTKNLNVSISKKRKRRFLGFLLGVGSAIASGIAVC K VLHLEGEVNKIKNALLSTNKAVVSLSNGVSVLT F KVLDLKNYINNQLLPI LNQQSCRISNIETVIEFQQKNSRLLEINREFSVNAGVTTPLSTYMLINSELLSLINDMPITNDQKKLMSSNVQIVRQQSYSIM CIIKEEVLAYVVOLPIYGVIDTPCWKLHTSPLCTTNIKEGSNICLTRTDRGWYCDNAGSVSFFPQADTCKVQSNRVFCDTMNSLTLPSEVSLCNTDIFNSKYDCKIMTSKTDISSSVITSLGAIVSCYGKTKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKLEGKNLYVKGEPIINYYDPLVFPSDEFDASISQVNEKINQSLAFIRRSDELLSAIGGYIPEAPRDGQAYVRKDGEWVLLSTFLGGLVPRGSHHHHHHSAWSHPQFEK (RSV_B F (+) FdTHS DSCav1)

-   -   SEQ ID NO: 373 is the amino acid sequence of a recombinant RSV F        protein from bovine RSV including S155C, S290C, S190F and V207L        amino acid substitutions, fused to a C-terminal Foldon domain,        thrombin cleavage site, 6×His tag and a StrepTag II. The four        mutated residues, and the C-terminal appendage are underlined.

MAATAMRMIISIIFISTYMTHITLCQNITEEFYQSTCSAVSRGYLSALRTGWYTSVVTIELSKIQKNVCKSTDSKVKLIKQELERYNNAVIELQSLMQNEPASFSRAKRGIPELIHYTRNSTKRFYGLMGKKRKRRFLGFLLGIGSAIASGVAVC K VLHLEGEVNKIKNALLSTNKAVVSLSNGVSVLT F KVLDLKNYIDKELLPK LNNHDCRISNIETVIEFQQKNNRLLEIAREFSVNAGITTPLSTYMLINSELLSLINDMPITNDQKKLMSSNVQIVRQQSYSIM CVVKEEVIAYVVQLPIYGVIDTPCWKLHTSPLCTTDNKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTMNSLTLPTDVNLCNTDIFNTKYDCKIMTSKTDISSSVITSIGAIVSCYGKTKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKLEGKALYIKGEPIINYYDPLVFPSDEFDASIAQVNAKINQSLAFIRRSDELLSAIGGYIPEAPRDGQAYVRKDGEWVLLSTFLGGLVPRGSHHHHHHSAWSHPQFEK (bRSV F (+) FdTHS DSCav1)

-   -   SEQ ID NO: 374 is the amino acid sequence of a recombinant RSV F        protein from human subtype A including S155C, S290C, and S190F        amino acid substitutions, fused to a C-terminal Foldon domain,        thrombin cleavage site, 6×His tag and a StrepTag II. The three        mutated residues, and the C-terminal appendage are underlined.    -   SEQ ID NO: 375 is the amino acid sequence of a recombinant RSV F        protein from human subtype B including S155C, S290C, and S190F        amino acid substitutions, fused to a C-terminal Foldon domain,        thrombin cleavage site, 6×His tag and a StrepTag II (RSV_B        F(+)FdTHS DSS190F)    -   SEQ ID NO: 376 is the amino acid sequence of a recombinant RSV F        protein from bovine RSV including S155C, S290C, and S190F amino        acid substitutions, fused to a C-terminal Foldon domain,        thrombin cleavage site, 6×His tag and a StrepTag II. (bRSV        F(+)FdTHS DSS190F)    -   SEQ ID NO: 377 is the amino acid sequence of a recombinant RSV F        protein from RSV A including S155C, S290C, S190F, V207L amino        acid substitutions, fused to a C-terminal ferritin domain.        (RSV_A F(+)FdTHS DSCav1 Ferritin)    -   SEQ ID NO: 378 is the amino acid sequence of a recombinant RSV F        protein from RSV B including 50 S155C, S290C, S190F, V207L amino        acid substitutions, fused to a C-terminal ferritin domain.        (RSV_B F(+)FdTHS DSCav1 ferritin)    -   SEQ ID NO: 379 is the amino acid sequence of a recombinant RSV F        protein from bRSV including S155C, S290C, S190F, V207L amino        acid substitutions, fused to a C-terminal ferritin domain. (bRSV        F(+)FdTHS DSCav1 ferritin)    -   SEQ ID NO: 380 is the amino acid sequence of a recombinant RSV F        protein from RSV A including S155C, S290C, S190F amino acid        substitutions, fused to a C-terminal ferritin domain. (RSV_A        F(+)FdTHS DSS190F Ferritin)    -   SEQ ID NO: 381 is the amino acid sequence of a recombinant RSV F        protein from RSV B including S155C, S290C, S190F amino acid        substitutions, fused to a C-terminal ferritin domain. (RSV_B        F(+)FdTHS DSS190F ferritin)    -   SEQ ID NO: 382 is the amino acid sequence of a recombinant RSV F        protein from bRSV including S155C, S290C, S190F amino acid        substitutions, fused to a C-terminal ferritin domain. (bRSV        F(+)FdTHS DSS190F ferritin)    -   SEQ ID NO: 383 is an exemplary nucleotide sequence encoding a        recombinant RSV F protein from human subtype A including S155C,        S290C, S190F and V207L amino acid substitutions, fused to a        C-terminal Foldon domain, thrombin cleavage site, 6×His tag and        a StrepTag II (DNA encoding RSV_A F(+)FdTHS DSCav1 expressed        from VRC3798).    -   SEQ ID NO: 384 is a nucleotide sequence of an expression vector        for expressing recombinant RSV F protein from human subtype A        including S155C, S290C, S190F and V207L amino acid        substitutions, fused to a C-terminal Foldon domain, thrombin        cleavage site, 6×His tag and a StrepTag II (RSV_A F(+)FdTHS        DSCav1 paH vector; VRC3798).    -   SEQ ID NO: 385 is an exemplary nucleotide sequence encoding a        recombinant RSV F protein from human subtype B (strain B1)        including S155C, S290C, S190F and V207L amino acid        substitutions, fused to a C-terminal Foldon domain, thrombin        cleavage site, 6×His tag and a StrepTag II (DNA encoding RSV_B        (B1) F(+)FdTHS DSCav1; expressed from VRC3764).    -   SEQ ID NO: 386 is a nucleotide sequence of an expression vector        for expressing recombinant RSV F protein from human subtype B        (strain B1) including S155C, S290C, S190F and V207L amino acid        substitutions, fused to a C-terminal Foldon domain, thrombin        cleavage site, 6×His tag and a StrepTag II (RSV_B (B1) F(+)FdTHS        DSCav1 paH vector; VRC3764).    -   SEQ ID NO: 387 is an exemplary nucleotide sequence encoding a        recombinant RSV F protein from human subtype B (Strain 18537)        including S155C, S290C, S190F and V207L amino acid        substitutions, fused to a C-terminal Foldon domain, thrombin        cleavage site, 6×His tag and a StrepTag II (DNA encoding RSV_B        F(+)FdTHS DSCav1; expressed from VRC3799).    -   SEQ ID NO: 388 is a nucleotide sequence of an expression vector        for expressing recombinant RSV F protein from human subtype B        (Strain 18537) including S155C, S290C, S190F and V207L amino        acid substitutions, fused to a C-terminal Foldon domain,        thrombin cleavage site, 6×His tag and a StrepTag II (RSV_B        F(+)FdTHS DSCav1 paH vector; VRC3799).    -   SEQ ID NOs: 389-693 are the amino acid sequences of recombinant        RSV F proteins stabilized in a prefusion conformation.    -   SEQ ID NOs: 694-697 are the amino acid sequences of modified        Foldon domain polypeptides.    -   SEQ ID NOs: 698-697 are the amino acid sequences of modified        Foldon domain polypeptides.    -   SEQ ID NOs: 698-828, 1429-1442 and 1474-1478 are the amino acid        sequences of single chain recombinant RSV F proteins.    -   SEQ ID NOs: 829-1025 and 1456-1468 are the amino acid sequences        of recombinant RSV F proteins linked to a cleavable foldon        domain, or not linked to a foldon domain.    -   SEQ ID NO: 1026 is the amino acid sequence of a RSV F protein        without prefusion-stabilizing substitutions.    -   SEQ ID NOs: 901-968 are the amino acid sequences of recombinant        RSV F proteins stabilized in a prefusion conformation.    -   SEQ ID NOs: 1027-1088 and 1099-1428 are the amino acid sequences        of minimal site Ø immunogens that are described in Example 14.

STRUCTURAL COORDINATES

The atomic coordinates of the crystal structure of RSV F protein boundby D25 Fab are recited in Table 1, which is submitted as an ASCII textfile in the form of the file named “Table_1.txt” (˜1 MB), which wascreated on Mar. 13, 2013, and is incorporated by reference herein, andwhich are also recited in Table 1 of U.S. Provisional Application No.61/780,910, filed Mar. 13, 2013, which is incorporated by referenceherein in its entirety. These atomic coordinates of the crystalstructure of RSV F protein bound by D25 Fab are also deposited asProtein Data Bank Accession No. 4JHW, and which is incorporated byreference herein as present in that database on May 1, 2013.

DETAILED DESCRIPTION

The RSV F glycoprotein it is a type I fusion protein that facilitatesfusion of viral and cellular membranes (Walsh and Hruska, J. Virol., 47,171 (1983)). After initial synthesis, RSV F adopts a metastableprefusion conformation that stores folding energy, which is releasedduring a structural rearrangement to a highly stable postfusionconformation after contact with host cell membranes. Three antigenicsites (I, II, and IV) on RSV F protein have been found to elicitneutralizing activity (Arbiza et al., J. Gen. Virol., 73, 2225 (1992);Lopez et al., J. Virol., 72, 6922 (1998); López et al., J. Virol., 64,927 (1990)), and all exist on the postfusion form of RSV F protein asdetermined by structural and biophysical studies (McLellan et al., J.Virol., 85, 7788 (2011); Swanson et al., Proc. Natl. Acad. Sci. U.S.A.,108, 9619 (2011)). Absorption of human sera with postfusion RSV F,however, fails to remove the majority of F-specific neutralizingactivity, suggesting that the prefusion form of RSV F harbors novelneutralizing antigenic sites (Magro et al., Proc. Natl. Acad. Sci.U.S.A., 109, 3089 (2012)).

Prior to the work disclosed herein, a homogeneous preparation of solubleprefusion RSV F protein was unavailable, precluding determination of theprefusion F structure and identification of novel prefusion F-specificantigenic sites. As described herein, RSV F protein specific antibodieswere identified that neutralize RSV, but do not specifically bind topostfusion RSV F, and the three-dimensional structure of prefusion F,recognized by these antibodies, was obtained. The results providedherein reveal for the first time the prefusion conformation of RSV F andthe mechanism of neutralization for a category of remarkably potent RSVprefusion F neutralizing antibodies. Using the three-dimensionalstructure of prefusion F as a guide, stabilized forms of prefusion F(“PreF” antigens) were constructed and used to generate RSV neutralizingimmune responses many fold greater than that achieved with prior RSV Fprotein-based immunogens.

I. TERMS

Unless otherwise noted, technical terms are used according toconventional usage. Definitions of common terms in molecular biology canbe found in Benjamin Lewin, Genes VII, published by Oxford UniversityPress, 1999; Kendrew et al. (eds.), The Encyclopedia of MolecularBiology, published by Blackwell Science Ltd., 1994; and Robert A. Meyers(ed.), Molecular Biology and Biotechnology: a Comprehensive DeskReference, published by VCH Publishers, Inc., 1995; and other similarreferences.

As used herein, the singular forms “a,” “an,” and “the,” refer to boththe singular as well as plural, unless the context clearly indicatesotherwise. For example, the term “an antigen” includes single or pluralantigens and can be considered equivalent to the phrase “at least oneantigen.” As used herein, the term “comprises” means “includes.” Thus,“comprising an antigen” means “including an antigen” without excludingother elements. It is further to be understood that any and all basesizes or amino acid sizes, and all molecular weight or molecular massvalues, given for nucleic acids or polypeptides are approximate, and areprovided for descriptive purposes, unless otherwise indicated. Althoughmany methods and materials similar or equivalent to those describedherein can be used, particular suitable methods and materials aredescribed herein. In case of conflict, the present specification,including explanations of terms, will control. In addition, thematerials, methods, and examples are illustrative only and not intendedto be limiting. To facilitate review of the various embodiments, thefollowing explanations of terms are provided:

5C4: A neutralizing monoclonal antibody that specifically binds to theprefusion conformation of the RSV F protein, but not to the post fusionconformation of RSV F protein. The κC4 antibody include heavy and lightchain variable regions with the amino acid sequences set forth as SEQ IDNOs: 1470 and 1471, respectively. As described in McLellan et al.,Science, 340(6136):1113-7, 2013, 5C4 specifically binds to a quaternaryepitope found on the RSV F protein in its prefusion conformation, butnot the post fusion conformation. In several embodiments, antibody 5C4specifically binds to the PreF antigens disclosed herein.

5C4 Heavy Chain Variable Domain: (SEQ ID NO: 1470)EVQLQQSGAELVKPGASVKLSCTASGFNIKDTFFHWVKQRPEQGLEWIGRIDPADGHTKYDPKFQGKATITADTSSNTAFLQLSSLTSVDTAVYYCATTITAVVPTPYNAMDYWGQGTSVTVSS 5C4 Kappa Light Chain Variable Domain:(SEQ ID NO: 1471) DIVLTQSPASLAVSLGQRTTISCRASESVDSFDNSFIHWYQQKPGQPPKLLIFLASSLESGVPARFSGSGSRTDFTLTIDPVEADDAATYYCQQSNED PFTFGSGTKLEIK

Adjuvant: A vehicle used to enhance antigenicity. Adjuvants include asuspension of minerals (alum, aluminum hydroxide, or phosphate) on whichantigen is adsorbed; or water-in-oil emulsion, for example, in whichantigen solution is emulsified in mineral oil (Freund incompleteadjuvant), sometimes with the inclusion of killed mycobacteria (Freund'scomplete adjuvant) to further enhance antigenicity (inhibits degradationof antigen and/or causes influx of macrophages). Immunostimulatoryoligonucleotides (such as those including a CpG motif) can also be usedas adjuvants. Adjuvants include biological molecules (a “biologicaladjuvant”), such as costimulatory molecules. Exemplary adjuvants includeIL-2, RANTES, GM-CSF, TNF-α, IFN-γ, G-CSF, LFA-3, CD72, B7-1, B7-2,OX-40L, 4-1BBL and toll-like receptor (TLR) agonists, such as TLR-9agonists. The person of ordinary skill in the art is familiar withadjuvants (see, e.g., Singh (ed.) Vaccine Adjuvants and DeliverySystems. Wiley-Interscience, 2007). Adjuvants can be used in combinationwith the disclosed PreF antigens.

Administration: The introduction of a composition into a subject by achosen route. Administration can be local or systemic. For example, ifthe chosen route is intravenous, the composition (such as a compositionincluding a disclosed immunogen) is administered by introducing thecomposition into a vein of the subject.

Agent: Any substance or any combination of substances that is useful forachieving an end or result; for example, a substance or combination ofsubstances useful for inhibiting RSV infection in a subject. Agentsinclude proteins, nucleic acid molecules, compounds, small molecules,organic compounds, inorganic compounds, or other molecules of interest,such as viruses, such as recombinant viruses. An agent can include atherapeutic agent (such as an anti-RSV agent), a diagnostic agent or apharmaceutical agent. In some embodiments, the agent is a polypeptideagent (such as an immunogenic RSV polypeptide), or an anti-viral agent.The skilled artisan will understand that particular agents may be usefulto achieve more than one result.

AM22: A neutralizing monoclonal antibody that specifically binds to theprefusion conformation of the RSV F protein, but not the post fusionconformation of RSV F protein. AM22 protein and nucleic acid sequencesare known, for example, the heavy and light chain amino acid sequencesof the AM22 antibody are set forth in U.S. Pat. App. Pub. No.2012/0070446, which is incorporated herein in its entirety). Asdescribed in Example 1, AM22 specifically binds to an epitope (includedon antigenic site Ø) including positions found on the RSV F protein inits prefusion conformation, but not the post fusion conformation. Thisepitope is included within RSV F positions 62-69 and 196-209, andlocated at the membrane distal apex of the RSV F protein in theprefusion conformation (see, e.g., FIGS. 2B and 9A). Prior to thisdisclosure it was not known that AM22 was specific for the prefusionconformation. In several embodiments, antibody AM22 specifically bindsto the PreF antigens disclosed herein.

Amino acid substitutions: The replacement of one amino acid in anantigen with a different amino acid or a deletion of an amino acid. Insome examples, an amino acid in an antigen is substituted with an aminoacid from a homologous protein.

Animal: A living multi-cellular vertebrate or invertebrate organism, acategory that includes, for example, mammals. The term mammal includesboth human and non-human mammals. Similarly, the term “subject” includesboth human and veterinary subjects, such as non-human primates. Thus,administration to a subject can include administration to a humansubject. Non-limiting examples of veterinary subjects includedomesticated animals (such as cats and dogs), livestock (for example,cattle, horses, pigs, sheep, and goats), and laboratory animals (forexample, mice, rabbits, rats, gerbils, guinea pigs, and non-humanprimates).

Antibody: A polypeptide that in nature is substantially encoded by animmunoglobulin gene or immunoglobulin genes, or fragments thereof, whichspecifically binds and recognizes an analyte (such as an antigen orimmunogen) such as a RSV F protein or antigenic fragment thereof.Immunoglobulin genes include the kappa, lambda, alpha, gamma, delta,epsilon and mu constant region genes, as well as the myriadimmunoglobulin variable region genes. The term “antibody,” as usedherein, includes antibody fragments produced, for example, by themodification of whole antibodies and by de novo synthesis usingrecombinant DNA methodologies.

Antibodies exist, for example, as intact immunoglobulins and as a numberof well characterized antibody fragments. For instance, Fabs, Fvs, andsingle-chain Fvs (SCFvs) that bind to RSV F protein, would be RSV Fprotein-specific binding agents. This includes intact immunoglobulinsand the variants and portions of them well known in the art, such asFab′ fragments, F(ab)′₂ fragments, single chain Fv proteins (“scFv”),and disulfide stabilized Fv proteins (“dsFv”). A scFv protein is afusion protein in which a light chain variable region of animmunoglobulin and a heavy chain variable region of an immunoglobulinare bound by a linker, while in dsFvs, the chains have been mutated tointroduce a disulfide bond to stabilize the association of the chains.The term also includes genetically engineered forms such as chimericantibodies (such as humanized murine antibodies), heteroconjugateantibodies (such as bispecific antibodies). See also, Pierce Catalog andHandbook, 1994-1995 (Pierce Chemical Co., Rockford, IL); Kuby, J.,Immunology, 3^(rd) Ed., W.H. Freeman & Co., New York, 1997.

Antibody fragments are defined as follows: (1) Fab, the fragment whichcontains a monovalent antigen-binding fragment of an antibody moleculeproduced by digestion of whole antibody with the enzyme papain to yieldan intact light chain and a portion of one heavy chain; (2) Fab′, thefragment of an antibody molecule obtained by treating whole antibodywith pepsin, followed by reduction, to yield an intact light chain and aportion of the heavy chain; two Fab′ fragments are obtained per antibodymolecule; (3) (Fab′)2, the fragment of the antibody obtained by treatingwhole antibody with the enzyme pepsin without subsequent reduction; (4)F(ab′)2, a dimer of two Fab′ fragments held together by two disulfidebonds; (5) Fv, a genetically engineered fragment containing the variableregion of the light chain and the variable region of the heavy chainexpressed as two chains; and (6) single chain antibody (“SCA”), agenetically engineered molecule containing the variable region of thelight chain, the variable region of the heavy chain, linked by asuitable polypeptide linker as a genetically fused single chainmolecule.

Typically, a naturally occurring immunoglobulin has heavy (H) chains andlight (L) chains interconnected by disulfide bonds. There are two typesof light chain, lambda (λ) and kappa (κ). There are five main heavychain classes (or isotypes) which determine the functional activity ofan antibody molecule: IgM, IgD, IgG, IgA and IgE. The disclosedantibodies can be class switched.

Each heavy and light chain contains a constant region and a variableregion, (the regions are also known as “domains”). In severalembodiments, the heavy and the light chain variable domains combine tospecifically bind the antigen. In additional embodiments, only the heavychain variable domain is required. For example, naturally occurringcamelid antibodies consisting of a heavy chain only are functional andstable in the absence of light chain (see, e.g., Hamers-Casterman etal., Nature, 363:446-448, 1993; Sheriff et al., Nat. Struct. Biol.,3:733-736, 1996). Light and heavy chain variable domains contain a“framework” region interrupted by three hypervariable regions, alsocalled “complementarity-determining regions” or “CDRs” (see, e.g., Kabatet al., Sequences of Proteins of Immunological Interest, U.S. Departmentof Health and Human Services, 1991). The sequences of the frameworkregions of different light or heavy chains are relatively conservedwithin a species. The framework region of an antibody, that is thecombined framework regions of the constituent light and heavy chains,serves to position and align the CDRs in three-dimensional space.

The CDRs are primarily responsible for binding to an epitope of anantigen. The amino acid sequence boundaries of a given CDR can bereadily determined using any of a number of well-known schemes,including those described by Kabat et al. (“Sequences of Proteins ofImmunological Interest,” 5th Ed. Public Health Service, NationalInstitutes of Health, Bethesda, M D, 1991; “Kabat” numbering scheme),Al-Lazikani et al., (JMB 273,927-948, 1997; “Chothia” numbering scheme),and Lefranc, et al. (“IMGT unique numbering for immunoglobulin and Tcell receptor variable domains and Ig superfamily V-like domains,” Dev.Comp. Immunol., 27:55-77, 2003; “IMGT” numbering scheme).

The CDRs of each chain are typically referred to as CDR1, CDR2, and CDR3(from the N-terminus to C-terminus), and are also typically identifiedby the chain in which the particular CDR is located. Thus, a V_(H) CDR3is located in the variable domain of the heavy chain of the antibody inwhich it is found, whereas a V_(L) CDR1 is the CDR1 from the variabledomain of the light chain of the antibody in which it is found. Lightchain CDRs are sometimes referred to as CDR L1, CDR L2, and CDR L3.Heavy chain CDRs are sometimes referred to as CDR H1, CDR H2, and CDRH3.

Antigen: A compound, composition, or substance that can stimulate theproduction of antibodies or a T cell response in an animal, includingcompositions that are injected or absorbed into an animal. An antigenreacts with the products of specific humoral or cellular immunity,including those induced by heterologous antigens, such as the disclosedrecombinant RSV F proteins.

Examples of antigens include, but are not limited to, polypeptides,peptides, lipids, polysaccharides, combinations thereof (such asglycopeptides) and nucleic acids containing antigenic determinants, suchas those recognized by an immune cell. In some examples, antigensinclude peptides derived from a pathogen of interest, such as RSV. Inspecific examples, an antigen is derived from RSV, such as an antigenincluding a modified RSV F protein stabilized in a prefusionconformation. “Epitope” or “antigenic determinant” refers to the regionof an antigen to which B and/or T cells respond.

Anti-RSV agent: An agent that specifically inhibits RSV from replicatingor infecting cells. Non-limiting examples of anti-RSV agents include themonoclonal antibody palivizumab (SYNAGIS®; Medimmune, Inc.) and thesmall molecule anti-viral drug ribavirin (manufactured by many sources,e.g., Warrick Pharmaceuticals, Inc.).

Atomic Coordinates or Structure coordinates: Mathematical coordinatesderived from mathematical equations related to the patterns obtained ondiffraction of a monochromatic beam of X-rays by the atoms (scatteringcenters) such as an antigen, or an antigen in complex with an antibody.In some examples that antigen can be RSV F protein (for examplestabilized in a prefusion conformation by binding to aprefusion-specific antibody, or by introduction of stabilizingmodifications) in a crystal. The diffraction data are used to calculatean electron density map of the repeating unit of the crystal. Theelectron density maps are used to establish the positions of theindividual atoms within the unit cell of the crystal. In one example,the term “structure coordinates” refers to Cartesian coordinates derivedfrom mathematical equations related to the patterns obtained ondiffraction of a monochromatic beam of X-rays, such as by the atoms of aRSV F protein in crystal form.

Those of ordinary skill in the art understand that a set of structurecoordinates determined by X-ray crystallography is not without standarderror. For the purpose of this disclosure, any set of structurecoordinates that have a root mean square deviation of protein backboneatoms (N, Cα, C and O) of less than about 1.0 Angstroms whensuperimposed, such as about 0.75, or about 0.5, or about 0.25 Angstroms,using backbone atoms, shall (in the absence of an explicit statement tothe contrary) be considered identical.

Cavity-filling amino acid substitution: An amino acid substitution thatfills a cavity within the protein core of the RSV F protein, for examplea cavity present in a protomer of the RSV F protein, or a cavity betweenprotomers of the RSV F protein. Cavities are essentially voids within afolded protein where amino acids or amino acid side chains are notpresent. In several embodiments, a cavity filling amino acidsubstitution is introduced to fill a cavity in the RSV F protein corepresent in the RSV F protein prefusion conformation that collapse (e.g.,have reduced volume) after transition to the postfusion conformation.

Circular Permutant: A modified recombinant protein in which theconnections between different regions of a protein tertiary structure ismodified, so that the relative order of different regions in the primarysequence is altered, but the placement of the regions in the tertiarystructure is preserved. For example, with a 4-stranded antiparallelsheet, with strand A, B, C and D, which has the following N and Ctermini and connectivity,

Nterm-strand A-linker-strand B-linker-strand C-linker-strand D-Cterm,

circular permutants of the 4 strands, A, B, C and D by altering linkerconnection between strands would includePermutation with N- and C-Termini Altered:

Nterm-strand C-linker-strand D-linker-strand A-linker-strand B-Cterm

Permutation with N terminus preserved:

Nterm-strand A-linker-strand D-linker-strand C-linker-strand B-C term

Permutation with C terminus preserved:

Nterm-strand C-linker-strand B-linker-strand A-linker-strand D-C term.

Contacting: Placement in direct physical association; includes both insolid and liquid form. Contacting includes contact between one moleculeand another molecule, for example the amino acid on the surface of onepolypeptide, such as an antigen, that contact another polypeptide, suchas an antibody. Contacting also includes administration, such asadministration of a disclosed antigen to a subject by a chosen route.

Control: A reference standard. In some embodiments, the control is anegative control sample obtained from a healthy patient. In otherembodiments, the control is a positive control sample obtained from apatient diagnosed with RSV infection. In still other embodiments, thecontrol is a historical control or standard reference value or range ofvalues (such as a previously tested control sample, such as a group ofRSV patients with known prognosis or outcome, or group of samples thatrepresent baseline or normal values).

A difference between a test sample and a control can be an increase orconversely a decrease. The difference can be a qualitative difference ora quantitative difference, for example a statistically significantdifference. In some examples, a difference is an increase or decrease,relative to a control, of at least about 5%, such as at least about 10%,at least about 20%, at least about 30%, at least about 40%, at leastabout 50%, at least about 60%, at least about 70%, at least about 80%,at least about 90%, at least about 100%, at least about 150%, at leastabout 200%, at least about 250%, at least about 300%, at least about350%, at least about 400%, at least about 500%, or greater than 500%.

D25: A neutralizing monoclonal antibody that specifically binds to theprefusion conformation of the RSV F protein, but not the post fusionconformation of RSV F protein. D25 protein and nucleic acid sequencesare known, for example, the heavy and light chain amino acid sequencesof the D25 antibody are set forth in U.S. Pat. App. Pub. No.2010/0239593, which is incorporated herein in its entirety; see also,Kwakkenbos et al., Nat. Med., 16:123-128, 2009). As described in Example1, D25 specifically binds to a quaternary epitope (included on antigenicsite Ø) found on the RSV F protein in its prefusion conformation, butnot the post fusion conformation. This epitope is included within RSV Fpositions 62-69 and 196-209, and located at the membrane distal apex ofthe RSV F protein in the prefusion conformation (see, e.g., FIGS. 2B and9A). Prior to this disclosure it was not known that D25 was specific forthe prefusion conformation of RSV F protein). In several embodiments,antibody D25 specifically binds to the PreF antigens disclosed herein.

Degenerate variant and conservative variant: A polynucleotide encoding apolypeptide that includes a sequence that is degenerate as a result ofthe genetic code. For example, a polynucleotide encoding a disclosedantigen, or an antibody that specifically binds a disclosed antigen,that includes a sequence that is degenerate as a result of the geneticcode. There are 20 natural amino acids, most of which are specified bymore than one codon. Therefore, all degenerate nucleotide sequences areincluded as long as the amino acid sequence of the antigen or antibodythat binds the antigen encoded by the nucleotide sequence is unchanged.Because of the degeneracy of the genetic code, a large number offunctionally identical nucleic acids encode any given polypeptide. Forinstance, the codons CGU, CGC, CGA, CGG, AGA, and AGG all encode theamino acid arginine. Thus, at every position where an arginine isspecified within a protein encoding sequence, the codon can be alteredto any of the corresponding codons described without altering theencoded protein. Such nucleic acid variations are “silent variations,”which are one species of conservative variations. Each nucleic acidsequence herein that encodes a polypeptide also describes every possiblesilent variation. One of skill will recognize that each codon in anucleic acid (except AUG, which is ordinarily the only codon formethionine) can be modified to yield a functionally identical moleculeby standard techniques. Accordingly, each “silent variation” of anucleic acid which encodes a polypeptide is implicit in each describedsequence.

One of ordinary skill will recognize that individual substitutions,deletions or additions which alter, add or delete a single amino acid ora small percentage of amino acids (for instance less than 5%, in someembodiments less than 1%) in an encoded sequence are conservativevariations where the alterations result in the substitution of an aminoacid with a chemically similar amino acid.

Conservative amino acid substitutions providing functionally similaramino acids are well known in the art. The following six groups eachcontain amino acids that are conservative substitutions for one another:

-   -   1) Alanine (A), Serine (S), Threonine (T);    -   2) Aspartic acid (D), Glutamic acid (E);    -   3) Asparagine (N), Glutamine (Q);    -   4) Arginine (R), Lysine (K);    -   5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V); and    -   6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W).

Not all residue positions within a protein will tolerate an otherwise“conservative” substitution. For instance, if an amino acid residue isessential for a function of the protein, even an otherwise conservativesubstitution may disrupt that activity, for example the specific bindingof an antibody to a target epitope may be disrupted by a conservativemutation in the target epitope.

Epitope: An antigenic determinant. These are particular chemical groupsor peptide sequences on a molecule that are antigenic, such that theyelicit a specific immune response, for example, an epitope is the regionof an antigen to which B and/or T cells respond. An antibody binds aparticular antigenic epitope, such as an epitope of a RSV F protein, forexample, a D25 or AM22 epitope present on the prefusion conformation ofthe RSV F protein.

Epitopes can be formed both from contiguous amino acids or noncontiguousamino acids juxtaposed by tertiary folding of a protein. Epitopes formedfrom contiguous amino acids are typically retained on exposure todenaturing solvents whereas epitopes formed by tertiary folding aretypically lost on treatment with denaturing solvents. An epitopetypically includes at least 3, and more usually, at least 5, about 9, orabout 8-10 amino acids in a unique spatial conformation. Methods ofdetermining spatial conformation of epitopes include, for example, x-raycrystallography and nuclear magnetic resonance. Epitopes can alsoinclude post-translation modification of amino acids, such as N-linkedglycosylation.

In one embodiment, T cells respond to the epitope, when the epitope ispresented in conjunction with an MHC molecule. Epitopes can be formedboth from contiguous amino acids or noncontiguous amino acids juxtaposedby tertiary folding of a protein. Epitopes formed from contiguous aminoacids are typically retained on exposure to denaturing solvents whereasepitopes formed by tertiary folding are typically lost on treatment withdenaturing solvents. An epitope typically includes at least 3, and moreusually, at least 5, about 9, or about 8-10 amino acids in a uniquespatial conformation. Methods of determining spatial conformation ofepitopes include, for example, x-ray crystallography and nuclearmagnetic resonance.

A “target epitope” is a particular epitope on an antigen thatspecifically binds an antibody of interest, such as a monoclonalantibody. In some examples, a target epitope includes the amino acidresidues that contact the antibody of interest, such that the targetepitope can be selected by the amino acid residues determined to be incontact with the antibody of interest.

Effective amount: An amount of agent, such as a PreF antigen or nucleicacid encoding a PreF antigen or other agent that is sufficient togenerate a desired response, such as an immune response to RSV Fprotein, or a reduction or elimination of a sign or symptom of acondition or disease, such as RSV infection. For instance, this can bethe amount necessary to inhibit viral replication or to measurably alteroutward symptoms of the viral infection. In general, this amount will besufficient to measurably inhibit virus (for example, RSV) replication orinfectivity. When administered to a subject, a dosage will generally beused that will achieve target tissue concentrations (for example, inrespiratory tissue) that has been shown to achieve in vitro inhibitionof viral replication. In some examples, an “effective amount” is onethat treats (including prophylaxis) one or more symptoms and/orunderlying causes of any of a disorder or disease, for example to treatRSV infection. In one example, an effective amount is a therapeuticallyeffective amount. In one example, an effective amount is an amount thatprevents one or more signs or symptoms of a particular disease orcondition from developing, such as one or more signs or symptomsassociated with RSV infection.

Expression: Translation of a nucleic acid into a protein. Proteins maybe expressed and remain intracellular, become a component of the cellsurface membrane, or be secreted into the extracellular matrix ormedium.

Expression Control Sequences: Nucleic acid sequences that regulate theexpression of a heterologous nucleic acid sequence to which it isoperatively linked. Expression control sequences are operatively linkedto a nucleic acid sequence when the expression control sequences controland regulate the transcription and, as appropriate, translation of thenucleic acid sequence. Thus expression control sequences can includeappropriate promoters, enhancers, transcription terminators, a startcodon (ATG) in front of a protein-encoding gene, splicing signal forintrons, maintenance of the correct reading frame of that gene to permitproper translation of mRNA, and stop codons. The term “controlsequences” is intended to include, at a minimum, components whosepresence can influence expression, and can also include additionalcomponents whose presence is advantageous, for example, leader sequencesand fusion partner sequences. Expression control sequences can include apromoter.

A promoter is a minimal sequence sufficient to direct transcription.Also included are those promoter elements which are sufficient to renderpromoter-dependent gene expression controllable for cell-type specific,tissue-specific, or inducible by external signals or agents; suchelements may be located in the 5′ or 3′ regions of the gene. Bothconstitutive and inducible promoters are included (see for example,Bitter et al., Methods in Enzymology 153:516-544, 1987). For example,when cloning in bacterial systems, inducible promoters such as pL ofbacteriophage lambda, plac, ptrp, ptac (ptrp-lac hybrid promoter) andthe like may be used. In one embodiment, when cloning in mammalian cellsystems, promoters derived from the genome of mammalian cells (such asmetallothionein promoter) or from mammalian viruses (such as theretrovirus long terminal repeat; the adenovirus late promoter; thevaccinia virus 7.5K promoter) can be used. Promoters produced byrecombinant DNA or synthetic techniques may also be used to provide fortranscription of the nucleic acid sequences.

A polynucleotide can be inserted into an expression vector that containsa promoter sequence, which facilitates the efficient transcription ofthe inserted genetic sequence of the host. The expression vectortypically contains an origin of replication, a promoter, as well asspecific nucleic acid sequences that allow phenotypic selection of thetransformed cells.

Ferritin: A protein that stores iron and releases it in a controlledfashion. The protein is produced by almost all living organisms.Ferritin assembles into a globular protein complex that in some casesconsists of 24 protein subunits. In some examples, ferritin is used toform a nanoparticle presenting antigens on its surface, for example anRSV antigen, such as the disclosed RSV F protein antigens stabilized ina prefusion conformation.

Foldon domain: An amino acid sequence that naturally forms a trimericstructure. In some examples, a Foldon domain can be included in theamino acid sequence of a disclosed RSV F protein antigen stabilized in aprefusion conformation so that the antigen will form a trimer. In oneexample, a Foldon domain is the T4 Foldon domain set forth as SEQ ID NO:351 (GYIPEAPRDGQAYVRKDGEWVLLSTF). Several embodiments include a Foldondomain that can be cleaved from a purified protein, for example byincorporation of a thrombin cleave site adjacent to the Foldon domainthat can be used for cleavage purposes.

Glycoprotein (gp): A protein that contains oligosaccharide chains(glycans) covalently attached to polypeptide side-chains. Thecarbohydrate is attached to the protein in a cotranslational orposttranslational modification. This process is known as glycosylation.In proteins that have segments extending extracellularly, theextracellular segments are often glycosylated. Glycoproteins are oftenimportant integral membrane proteins, where they play a role incell-cell interactions. In some examples a glycoprotein is an RSVglycoprotein, such as a RSV F protein antigen stabilized in a prefusionconformation or an immunogenic fragment thereof.

Glycosylation site: An amino acid sequence on the surface of apolypeptide, such as a protein, which accommodates the attachment of aglycan. An N-linked glycosylation site is triplet sequence of NX(S/T) inwhich N is asparagine, X is any residues except proline, and (S/T) is aserine or threonine residue. A glycan is a polysaccharide oroligosaccharide. Glycan may also be used to refer to the carbohydrateportion of a glycoconjugate, such as a glycoprotein, glycolipid, or aproteoglycan.

Homologous proteins: Proteins that have a similar structure andfunction, for example, proteins from two or more species or viralstrains that have similar structure and function in the two or morespecies or viral strains. For example a RSV F protein from RSV A is ahomologous protein to a RSV F protein from bovine RSV. Homologousproteins share similar protein folding characteristics and can beconsidered structural homologs.

Homologous proteins typically share a high degree of sequenceconservation, such as at least 80%, at least 90%, at least 91%, at least92%, at least 93%, at least 94%, or at least 95%, at least 96%, at least97%, at least 98%, or at least 99% sequence conservation, and a highdegree of sequence identity, such as at least 80%, at least 90%, atleast 91%, at least 92%, at least 93%, at least 94%, or at least 95%, atleast 96%, at least 97%, at least 98%, or at least 99% sequenceidentity.

Host cells: Cells in which a vector can be propagated and its DNAexpressed. The cell may be prokaryotic or eukaryotic. The term alsoincludes any progeny of the subject host cell. It is understood that allprogeny may not be identical to the parental cell since there may bemutations that occur during replication. However, such progeny areincluded when the term “host cell” is used.

Immunogen: A protein or a portion thereof that is capable of inducing animmune response in a mammal, such as a mammal infected or at risk ofinfection with a pathogen. Administration of an immunogen can lead toprotective immunity and/or proactive immunity against a pathogen ofinterest. In some examples, an immunogen includes a disclosed PreFantigen.

Immune response: A response of a cell of the immune system, such as a Bcell, T cell, or monocyte, to a stimulus. In one embodiment, theresponse is specific for a particular antigen (an “antigen-specificresponse”). In one embodiment, an immune response is a T cell response,such as a CD4+ response or a CD8+ response. In another embodiment, theresponse is a B cell response, and results in the production of specificantibodies.

A “Th1” biased immune response is characterized by the presence of CD4⁺T helper cells that produce IL-2 and IFN-γ, and thus, by the secretionor presence of IL-2 and IFN-γ. In contrast, a “Th2” biased immuneresponse is characterized by a preponderance of CD4⁺ helper cells thatproduce IL-4, IL-5, and IL-13.

Immunogenic composition: A composition comprising an antigen thatinduces an immune response, such as a measurable CTL response againstvirus expressing the antigen, or a measurable B cell response (such asproduction of antibodies) against the antigen. As such, an immunogeniccomposition includes one or more antigens (for example, polypeptideantigens) or antigenic epitopes. An immunogenic composition can alsoinclude one or more additional components capable of eliciting orenhancing an immune response, such as an excipient, carrier, and/oradjuvant. In certain instances, immunogenic compositions areadministered to elicit an immune response that protects the subjectagainst symptoms or conditions induced by a pathogen. In some cases,symptoms or disease caused by a pathogen is prevented (or reduced orameliorated) by inhibiting replication of the pathogen (e.g., RSV)following exposure of the subject to the pathogen. In one example, an“immunogenic composition” includes a recombinant RSV F proteinstabilized in a prefusion conformation, that induces a measurable CTLresponse against virus expressing RSV F protein, or induces a measurableB cell response (such as production of antibodies) against RSV Fprotein. It further refers to isolated nucleic acids encoding anantigen, such as a nucleic acid that can be used to express the antigen(and thus be used to elicit an immune response against thispolypeptide).

For in vitro use, an immunogenic composition may include an antigen ornucleic acid encoding an antigen. For in vivo use, the immunogeniccomposition will typically include the protein, immunogenic peptide ornucleic acid in pharmaceutically acceptable carriers, and/or otheragents. Any particular peptide, such as a disclosed RSV F proteinstabilized in a prefusion conformation or a nucleic acid encoding adisclosed RSV F protein stabilized in a prefusion conformation, can bereadily tested for its ability to induce a CTL or B cell response byart-recognized assays. Immunogenic compositions can include adjuvants,which are well known to one of skill in the art.

Immunologically reactive conditions: Includes reference to conditionswhich allow an antibody raised against a particular epitope to bind tothat epitope to a detectably greater degree than, and/or to thesubstantial exclusion of, binding to substantially all other epitopes.Immunologically reactive conditions are dependent upon the format of theantibody binding reaction and typically are those utilized inimmunoassay protocols or those conditions encountered in vivo. Theimmunologically reactive conditions employed in the methods are“physiological conditions” which include reference to conditions (suchas temperature, osmolarity, pH) that are typical inside a living mammalor a mammalian cell. While it is recognized that some organs are subjectto extreme conditions, the intra-organismal and intracellularenvironment is normally about pH 7 (such as from pH 6.0 to pH 8.0, moretypically pH 6.5 to 7.5), contains water as the predominant solvent, andexists at a temperature above 0° C. and below 50° C. Osmolarity iswithin the range that is supportive of cell viability and proliferation.

Immunological probe: A molecule that can be used for selection ofantibodies from sera which are directed against a specific epitope orantigen, including from human patient sera. In some examples, thedisclosed RSV F proteins stabilized in a prefusion conformation can beused as immunological probes in both positive and negative selection ofantibodies specific for RSV F protein in a prefusion conformation.

Immunogenic surface: A surface of a molecule, for example RSV F protein,capable of eliciting an immune response. An immunogenic surface includesthe defining features of that surface, for example the three-dimensionalshape and the surface charge. In some examples, an immunogenic surfaceis defined by the amino acids on the surface of a protein or peptidethat are in contact with an antibody, such as a neutralizing antibody,when the protein and the antibody are bound together. A target epitopeincludes an immunogenic surface. Immunogenic surface is synonymous withantigenic surface.

Inhibiting or treating a disease: Inhibiting the full development of adisease or condition, for example, in a subject who is at risk for adisease, such as RSV infection. “Treatment” refers to a therapeuticintervention that ameliorates a sign or symptom of a disease orpathological condition after it has begun to develop. The term“ameliorating,” with reference to a disease or pathological condition,refers to any observable beneficial effect of the treatment. Thebeneficial effect can be evidenced, for example, by a delayed onset ofclinical symptoms of the disease in a susceptible subject, a reductionin severity of some or all clinical symptoms of the disease, a slowerprogression of the disease, an improvement in the overall health orwell-being of the subject, or by other parameters well known in the artthat are specific to the particular disease. A “prophylactic” treatmentis a treatment administered to a subject who does not exhibit signs of adisease or exhibits only early signs for the purpose of decreasing therisk of developing pathology.

The term “reduces” is a relative term, such that an agent reduces aresponse or condition if the response or condition is quantitativelydiminished following administration of the agent, or if it is diminishedfollowing administration of the agent, as compared to a reference agent.Similarly, the term “prevents” does not necessarily mean that an agentcompletely eliminates the response or condition, so long as at least onecharacteristic of the response or condition is eliminated. Thus, animmunogenic composition that reduces or prevents an infection or aresponse, such as a pathological response, e.g., vaccine enhanced viraldisease, can, but does not necessarily completely eliminate such aninfection or response, so long as the infection or response ismeasurably diminished, for example, by at least about 50%, such as by atleast about 70%, or about 80%, or even by about 90% of (that is to 10%or less than) the infection or response in the absence of the agent, orin comparison to a reference agent.

Isolated: An “isolated” biological component (such as a protein, forexample a disclosed PreF antigen or nucleic acid encoding such anantigen) has been substantially separated or purified away from otherbiological components, such as other biological components in which thecomponent naturally occurs, such as other chromosomal andextrachromosomal DNA, RNA, and proteins. Proteins, peptides and nucleicacids that have been “isolated” include proteins purified by standardpurification methods. The term also embraces proteins or peptidesprepared by recombinant expression in a host cell as well as chemicallysynthesized proteins, peptides and nucleic acid molecules. Isolated doesnot require absolute purity, and can include protein, peptide, ornucleic acid molecules that are at least 50% isolated, such as at least75%, 80%, 90%, 95%, 98%, 99%, or even 99.9% isolated. The PreF antigensdisclosed herein (for example, an isolated recombinant RSV F proteinstabilized in a prefusion conformation) are isolated from RSV F proteinsin a post-fusion conformation, for example, are at least 80% isolated,at least 90%, 95%, 98%, 99%, or even 99.9% isolated from RSV F proteinsin a postfusion conformation. In several embodiments, the PreF antigenis substantially separated from RSV F proteins that do not includeantigen site Ø and/or are not specifically bound by a prefusion specificmonoclonal antibody (such as D25 or AM22), for example, the PreF antigenmay be at least 80% isolated, at least 90%, 95%, 98%, 99%, or even 99.9%isolated from RSV F proteins that do not include antigen site Ø and/orare not specifically bound by a prefusion specific monoclonal antibody,such as D25 or AM22.

K_(d): The dissociation constant for a given interaction, such as apolypeptide-ligand interaction or an antibody-antigen interaction. Forexample, for the bimolecular interaction of an antibody (such as D25)and an antigen (such as RSV F protein), it is the concentration of theindividual components of the bimolecular interaction divided by theconcentration of the complex. Methods of determining the K_(d) of anantibody:antigen interaction are familiar to the person of ordinaryskill in the art.

Label: A detectable compound or composition that is conjugated directlyor indirectly to another molecule to facilitate detection of thatmolecule. Specific, non-limiting examples of labels include fluorescenttags, enzymatic linkages, and radioactive isotopes. In some examples, adisclosed PreF antigen is labeled with a detectable label. In someexamples, label is attached to a disclosed antigen or nucleic acidencoding such an antigen.

Linker: A bi-functional molecule that can be used to link two or moremolecules into one contiguous molecule, for example, to link a carriermolecule to a immunogenic polypeptide. Non-limiting examples of peptidelinkers include a (G₄S)₁, (G₄S)₂, or a (G₄S)₃ peptide linker.

The terms “conjugating,” “joining,” “bonding,” or “linking” can refer tomaking two molecules into one contiguous molecule; for example, linkingtwo other polypeptides into one contiguous polypeptide, or covalentlyattaching a carrier molecule or other molecule to an immunogenicpolypeptide, such as an recombinant RSV F protein as disclosed herein.The linkage can be either by chemical or recombinant means. “Chemicalmeans” refers to a reaction, for example, between the immunogenicpolypeptide moiety and the carrier molecule such that there is acovalent bond formed between the two molecules to form one molecule.

MPE8: A neutralizing monoclonal antibody that specifically binds to theprefusion conformation of the RSV F protein, but not to the post fusionconformation of RSV F protein. As described in Corti et al. (Nature,501(7467)439-443, 2013, incorporated by reference herein in itsentirety) the MPE8 antibody binds to an epitope found on the pre-, butnot post-, fusion conformations of the RSV F protein. The MPE8 epitopeis not part of antigenic site Ø. The heavy and light chain variableregion sequences are set forth as SEQ ID NOs: 1472 and 1473,respectively.

Native antigen or native sequence: An antigen or sequence that has notbeen modified by selective mutation, for example, selective mutation tofocus the antigenicity of the antigen to a target epitope. Nativeantigen or native sequence are also referred to as wild-type antigen orwild-type sequence.

Nucleic acid: A polymer composed of nucleotide units (ribonucleotides,deoxyribonucleotides, related naturally occurring structural variants,and synthetic non-naturally occurring analogs thereof) linked viaphosphodiester bonds, related naturally occurring structural variants,and synthetic non-naturally occurring analogs thereof. Thus, the termincludes nucleotide polymers in which the nucleotides and the linkagesbetween them include non-naturally occurring synthetic analogs, such as,for example and without limitation, phosphorothioates, phosphoramidates,methyl phosphonates, chiral-methyl phosphonates, 2-O-methylribonucleotides, peptide-nucleic acids (PNAs), and the like. Suchpolynucleotides can be synthesized, for example, using an automated DNAsynthesizer. The term “oligonucleotide” typically refers to shortpolynucleotides, generally no greater than about 50 nucleotides. It willbe understood that when a nucleotide sequence is represented by a DNAsequence (i.e., A, T, G, C), this also includes an RNA sequence (i.e.,A, U, G, C) in which “U” replaces “T.”

“Nucleotide” includes, but is not limited to, a monomer that includes abase linked to a sugar, such as a pyrimidine, purine or syntheticanalogs thereof, or a base linked to an amino acid, as in a peptidenucleic acid (PNA). A nucleotide is one monomer in a polynucleotide. Anucleotide sequence refers to the sequence of bases in a polynucleotide.

Conventional notation is used herein to describe nucleotide sequences:the left-hand end of a single-stranded nucleotide sequence is the5′-end; the left-hand direction of a double-stranded nucleotide sequenceis referred to as the 5-direction. The direction of 5′ to 3′ addition ofnucleotides to nascent RNA transcripts is referred to as thetranscription direction. The DNA strand having the same sequence as anmRNA is referred to as the “coding strand;” sequences on the DNA strandhaving the same sequence as an mRNA transcribed from that DNA and whichare located 5′ to the 5′-end of the RNA transcript are referred to as“upstream sequences;” sequences on the DNA strand having the samesequence as the RNA and which are 3′ to the 3′ end of the coding RNAtranscript are referred to as “downstream sequences.”

“cDNA” refers to a DNA that is complementary or identical to an mRNA, ineither single stranded or double stranded form.

“Encoding” refers to the inherent property of specific sequences ofnucleotides in a polynucleotide, such as a gene, a cDNA, or an mRNA, toserve as templates for synthesis of other polymers and macromolecules inbiological processes having either a defined sequence of nucleotides(for example, rRNA, tRNA and mRNA) or a defined sequence of amino acidsand the biological properties resulting therefrom. Thus, a gene encodesa protein if transcription and translation of mRNA produced by that geneproduces the protein in a cell or other biological system. Both thecoding strand, the nucleotide sequence of which is identical to the mRNAsequence and is usually provided in sequence listings, and non-codingstrand, used as the template for transcription, of a gene or cDNA can bereferred to as encoding the protein or other product of that gene orcDNA. Unless otherwise specified, a “nucleotide sequence encoding anamino acid sequence” includes all nucleotide sequences that aredegenerate versions of each other and that encode the same amino acidsequence. Nucleotide sequences that encode proteins and RNA may includeintrons. In some examples, a nucleic acid encodes a disclosed PreFantigen.

Operably linked: A first nucleic acid sequence is operably linked with asecond nucleic acid sequence when the first nucleic acid sequence isplaced in a functional relationship with the second nucleic acidsequence. For instance, a promoter is operably linked to a codingsequence if the promoter affects the transcription or expression of thecoding sequence. Generally, operably linked DNA sequences are contiguousand, where necessary to join two protein-coding regions, in the samereading frame.

Prefusion-specific antibody: An antibody that specifically binds to theRSV F protein in a prefusion conformation, but does not specificallybinds to the RSV F protein in a post-fusion conformation. Exemplaryprefusion specific antibodies include the D25, AM22, 5C4 and MPE8antibodies

Polypeptide: Any chain of amino acids, regardless of length orpost-translational modification (such as glycosylation orphosphorylation). “Polypeptide” applies to amino acid polymers includingnaturally occurring amino acid polymers and non-naturally occurringamino acid polymer as well as in which one or more amino acid residue isa non-natural amino acid, for example an artificial chemical mimetic ofa corresponding naturally occurring amino acid. A “residue” refers to anamino acid or amino acid mimetic incorporated in a polypeptide by anamide bond or amide bond mimetic. A polypeptide has an amino terminal(N-terminal) end and a carboxy terminal (C-terminal) end. “Polypeptide”is used interchangeably with peptide or protein, and is usedinterchangeably herein to refer to a polymer of amino acid residues.

A single contiguous polypeptide chain of amino acid residues can includemultiple polypeptides. For example, the RSV F₀ polypeptide includes aN-terminal signal peptide, a F₂ polypeptide, a pep27 polypeptide, and aF₁ polypeptide including the F₁ extracellular domain, transmembranedomain and cytosolic tail. Further, in some embodiments a recombinantRSV F protein is a single chain RSV F protein including a RSV F₂polypeptide linked to a RSV F₁ polypeptide by a peptide linker.

In many instances, a polypeptide folds into a specific three-dimensionalstructure, and can include surface-exposed amino acid residues andnon-surface-exposed amino acid residues. In some instances a protein caninclude multiple polypeptides that fold together into a functional unit.For example, the RSV F protein is composed of F₁/F₂ heterodimers thattrimerize in to a multimeric protein. “Surface-exposed amino acidresidues” are those amino acids that have some degree of exposure on thesurface of the protein, for example such that they can contact thesolvent when the protein is in solution. In contrast,non-surface-exposed amino acids are those amino acid residues that arenot exposed on the surface of the protein, such that they do not contactsolution when the protein is in solution. In some examples, thenon-surface-exposed amino acid residues are part of the protein core.

A “protein core” is the interior of a folded protein, which issubstantially free of solvent exposure, such as solvent in the form ofwater molecules in solution. Typically, the protein core ispredominately composed of hydrophobic or apolar amino acids. In someexamples, a protein core may contain charged amino acids, for exampleaspartic acid, glutamic acid, arginine, and/or lysine. The inclusion ofuncompensated charged amino acids (a compensated charged amino can be inthe form of a salt bridge) in the protein core can lead to adestabilized protein. That is, a protein with a lower T_(m) then asimilar protein without an uncompensated charged amino acid in theprotein core. In other examples, a protein core may have a cavity withinthe protein core. Cavities are essentially voids within a folded proteinwhere amino acids or amino acid side chains are not present. Suchcavities can also destabilize a protein relative to a similar proteinwithout a cavity. Thus, when creating a stabilized form of a protein, itmay be advantageous to substitute amino acid residues within the core inorder to fill cavities present in the wild-type protein.

Amino acids in a peptide, polypeptide or protein generally arechemically bound together via amide linkages (CONH). Additionally, aminoacids may be bound together by other chemical bonds. For example,linkages for amino acids or amino acid analogs can include CH₂NH—,—CH₂S—, —CH₂—CH₂—, —CH═CH— (cis and trans), —COCH₂—, —CH(OH)CH₂—, and—CHH₂SO— (These and others can be found in Spatola, in Chemistry andBiochemistry of Amino Acids, Peptides, and Proteins, B. Weinstein, eds.,Marcel Dekker, New York, p. 267 (1983); Spatola, A. F., Vega Data (March1983), Vol. 1, Issue 3, Peptide Backbone Modifications (general review);Morley, Trends Pharm Sci pp. 463-468, 1980; Hudson, et al., Int J PeptProt Res 14:177-185, 1979; Spatola et al. Life Sci 38:1243-1249, 1986;Harm J. Chem. Soc Perkin Trans. 1307-314, 1982; Almquist et al. J. Med.Chem. 23:1392-1398, 1980; Jennings-White et al. Tetrahedron Lett23:2533, 1982; Holladay et al. Tetrahedron. Lett 24:4401-4404, 1983; andHruby Life Sci 31:189-199, 1982.

Peptide modifications: Peptides, such as the disclosed RSV F proteinsstabilized in a prefusion conformation can be modified, for example toinclude an amino acid substitution compared to a Native RSV proteinsequence, or by a variety of chemical techniques to produce derivativeshaving essentially the same activity and conformation as the unmodifiedpeptides, and optionally having other desirable properties. For example,carboxylic acid groups of the protein, whether carboxyl-terminal or sidechain, may be provided in the form of a salt of apharmaceutically-acceptable cation or esterified to form a C₁-C₁₆ ester,or converted to an amide of formula NR₁R₂ wherein R₁ and R₂ are eachindependently H or C₁-C₁₆ alkyl, or combined to form a heterocyclicring, such as a 5- or 6-membered ring. Amino groups of the peptide,whether amino-terminal or side chain, may be in the form of apharmaceutically-acceptable acid addition salt, such as the HCl, HBr,acetic, benzoic, toluene sulfonic, maleic, tartaric and other organicsalts, or may be modified to C₁-C₁₆ alkyl or dialkyl amino or furtherconverted to an amide.

Hydroxyl groups of the peptide side chains can be converted to C₁-C₁₆alkoxy or to a C₁-C₁₆ ester using well-recognized techniques. Phenyl andphenolic rings of the peptide side chains can be substituted with one ormore halogen atoms, such as F, Cl, Br or I, or with C₁-C₁₆ alkyl, C₁-C₁₆alkoxy, carboxylic acids and esters thereof, or amides of suchcarboxylic acids. Methylene groups of the peptide side chains can beextended to homologous C₂-C₄ alkylenes. Thiols can be protected with anyone of a number of well-recognized protecting groups, such as acetamidegroups.

Pharmaceutically acceptable carriers: The pharmaceutically acceptablecarriers of use are conventional. Remington's Pharmaceutical Sciences,by E. W. Martin, Mack Publishing Co., Easton, PA, 19th Edition, 1995,describes compositions and formulations suitable for pharmaceuticaldelivery of the disclosed immunogens.

In general, the nature of the carrier will depend on the particular modeof administration being employed. For instance, parenteral formulationsusually comprise injectable fluids that include pharmaceutically andphysiologically acceptable fluids such as water, physiological saline,balanced salt solutions, aqueous dextrose, glycerol or the like as avehicle. For solid compositions (e.g., powder, pill, tablet, or capsuleforms), conventional non-toxic solid carriers can include, for example,pharmaceutical grades of mannitol, lactose, starch, or magnesiumstearate. In addition to biologically neutral carriers, pharmaceuticalcompositions to be administered can contain minor amounts of non-toxicauxiliary substances, such as wetting or emulsifying agents,preservatives, and pH buffering agents and the like, for example sodiumacetate or sorbitan monolaurate. In particular embodiments, suitable foradministration to a subject the carrier may be sterile, and/or suspendedor otherwise contained in a unit dosage form containing one or moremeasured doses of the composition suitable to induce the desiredanti-RSV immune response. It may also be accompanied by medications forits use for treatment purposes. The unit dosage form may be, forexample, in a sealed vial that contains sterile contents or a syringefor injection into a subject, or lyophilized for subsequentsolubilization and administration or in a solid or controlled releasedosage.

Prime-boost vaccination: An immunotherapy including administration of afirst immunogenic composition (the primer vaccine) followed byadministration of a second immunogenic composition (the booster vaccine)to a subject to induce an immune response. The primer vaccine and/or thebooster vaccine include a vector (such as a viral vector, RNA, or DNAvector) expressing the antigen to which the immune response is directed.The booster vaccine is administered to the subject after the primervaccine; the skilled artisan will understand a suitable time intervalbetween administration of the primer vaccine and the booster vaccine,and examples of such timeframes are disclosed herein. In someembodiments, the primer vaccine, the booster vaccine, or both primervaccine and the booster vaccine additionally include an adjuvant. In onenon-limiting example, the primer vaccine is a DNA-based vaccine (orother vaccine based on gene delivery), and the booster vaccine is aprotein subunit or protein nanoparticle based vaccine.

Protein nanoparticle: A multi-subunit, protein-based polyhedron shapedstructure. The subunits are each composed of proteins or polypeptides(for example a glycosylated polypeptide), and, optionally of single ormultiple features of the following: nucleic acids, prosthetic groups,organic and inorganic compounds. Non-limiting examples of proteinnanoparticles include ferritin nanoparticles (see, e.g., Zhang, Y. Int.J. Mol. Sci., 12:5406-5421, 2011, incorporated by reference herein),encapsulin nanoparticles (see, e.g., Sutter et al., Nature Struct. andMol. Biol., 15:939-947, 2008, incorporated by reference herein), SulfurOxygenase Reductase (SOR) nanoparticles (see, e.g., Urich et al.,Science, 311:996-1000, 2006, incorporated by reference herein), lumazinesynthase nanoparticles (see, e.g., Zhang et al., J. Mol. Biol., 306:1099-1114, 2001) or pyruvate dehydrogenase nanoparticles (see, e.g.,Izard et al., PNAS 96: 1240-1245, 1999, incorporated by referenceherein). Ferritin, encapsulin, SOR, lumazine synthase, and pyruvatedehydrogenase are monomeric proteins that self-assemble into a globularprotein complexes that in some cases consists of 24, 60, 24, 60, and 60protein subunits, respectively. In some examples, ferritin, encapsulin,SOR, lumazine synthase, or pyruvate dehydrogenase monomers are linked toa disclosed antigen (for example, a recombinant RSV F protein stabilizedin a prefusion conformation) and self-assembled into a proteinnanoparticle presenting the disclosed antigens on its surface, which canbe administered to a subject to stimulate an immune response to theantigen.

Recombinant: A recombinant nucleic acid is one that has a sequence thatis not naturally occurring or has a sequence that is made by anartificial combination of two otherwise separated segments of sequence.This artificial combination can be accomplished by chemical synthesisor, more commonly, by the artificial manipulation of isolated segmentsof nucleic acids, for example, by genetic engineering techniques. Arecombinant protein is one that has a sequence that is not naturallyoccurring or has a sequence that is made by an artificial combination oftwo otherwise separated segments of sequence. In several embodiments, arecombinant protein is encoded by a heterologous (for example,recombinant) nucleic acid that has been introduced into a host cell,such as a bacterial or eukaryotic cell. The nucleic acid can beintroduced, for example, on an expression vector having signals capableof expressing the protein encoded by the introduced nucleic acid or thenucleic acid can be integrated into the host cell chromosome.

Repacking amino acid substitution: An amino acid substitution thatincreases the interactions of neighboring residues in a protein, forexample, by enhancing hydrophobic interactions or hydrogen-bondformation, or by reducing unfavorable or repulsive interactions ofneighboring residues, for example, by eliminating clusters of similarlycharged residues. In several embodiments, a repacking amino acidsubstitution is introduced to increase the interactions of neighboringresidues in the RSV F protein prefusion conformation, that are not inclose proximity in the RSV F postfusion conformation. Typically,introduction of a repacking amino acid substitution will increase theT_(m) of the prefusion conformation of the RSV F protein, and lower theT_(m) of the postfusion conformation of the RSV F protein.

Respiratory Syncytial Virus (RSV): An enveloped non-segmentednegative-sense single-stranded RNA virus of the family Paramyxoviridae.It is the most common cause of bronchiolitis and pneumonia amongchildren in their first year of life and infects nearly all children by3 years of age. RSV also causes repeated infections including severelower respiratory tract disease, which may occur at any age, especiallyamong the elderly or those with compromised cardiac, pulmonary, orimmune systems. In the United States, RSV bronchiolitis is the leadingcause of hospitalization in infants and a major cause of asthma andwheezing throughout childhood (Shay et al., JAMA, 282, 1440 (1999); Hallet al., N. Engl. J. Med., 360, 588 (2009)). Globally, RSV is responsiblefor 66,000-199,000 deaths each year for children younger than five yearsof age (Nair et al., Lancet, 375, 1545 (2010)), and accounts for 6.7% ofdeaths among infants one month to one year old-more than any othersingle pathogen except malaria (Lozano et al., Lancet, 380, 2095(2013)).

The RSV genome is ˜15,000 nucleotides in length and includes 10 genesencoding 11 proteins, including the glycoproteins SH, G and F. The Fprotein mediates fusion, allowing entry of the virus into the cellcytoplasm and also promoting the formation of syncytia. Two subtypes ofhuman RSV strains have been described, the A and B subtypes, based ondifferences in the antigenicity of the G glycoprotein. RSV strains forother species are also known, including bovine RSV. Exemplary RSV strainsequences are known to the person of ordinary skill in the art. Further,several models of human RSV infection are available, including modelorganisms infected with hRSV, as well as model organisms infected withspecies specific RSV, such as use of bRSV infection in cattle (see,e.g., Bern et al., Am J, Physiol. Lung Cell Mol. Physiol., 301:L148-L156, 2011).

Several methods of diagnosing RSV infection are known, including use ofDirect Fluorescent Antibody detection (DFA), Chromatographic rapidantigen detection, and detection of viral RNA using RT PCR.Quantification of viral load can be determined, for example, by PlaqueAssay, antigen capture enzyme immunoassay (EIA), or PCR. Quantificationof antibody levels can be performed by subtype-specific Neutralizationassay or ELISA. Current RSV treatment is passive administration of themonoclonal antibody palivizumab (SYNAGIS®), which recognizes the RSV Fprotein (Johnson et al., J. Infect. Dis., 176, 1215 (1997); Beeler andvan Wyke Coelingh, J. Virol., 63, 2941 (1989)) and reduces incidence ofsevere disease (The IMpact-RSV Study Group, Pediatrics, 102, 531(1998)). (Also see, e.g., Nam and Kun (Eds.). Respiratory SyncytialVirus: Prevention, Diagnosis and Treatment. Nova Biomedical Nova SciencePublisher, 2011; and Cane (Ed.) Respiratory Syncytial Virus. ElsevierScience, 2007.)

There are several subtypes of RSV, including human subtype A, humansubtype B, and bovine subtype. Within the subtypes of RSV, there areindividual strains of each subtype. For example, SEQ ID NOs: 1-128provided herein include RSV F protein sequences for many strains ofsubtype A RSV, which (as shown in Table 3 below) are highly homologous.

RSV Fusion (F) protein: An RSV envelope glycoprotein that facilitatesfusion of viral and cellular membranes. In nature, the RSV F protein isinitially synthesized as a single polypeptide precursor approximately574 amino acids in length, designated F₀. F₀ includes an N-terminalsignal peptide that directs localization to the endoplasmic reticulum,where the signal peptide (approximately the first 25 residues of F₀) isproteolytically cleaved. The remaining F₀ residues oligomerize to form atrimer which is again proteolytically processed by a cellular proteaseat two conserved furin consensus cleavage sequences (approximately F₀positions 109 and 136; for example, RARR₁₀₉ (SEQ ID NO: 124, residues106-109) and RKRR₁₃₆ (SEQ ID NO: 124, residues 133-136) to generate twodisulfide-linked fragments, F₁ and F₂. The smaller of these fragments,F₂, originates from the N-terminal portion of the F₀ precursor andincludes approximately residues 26-109 of F₀. The larger of thesefragments, F₁, includes the C-terminal portion of the F₀ precursor(approximately residues 137-574) including an extracellular/lumenalregion (˜residues 137-524), a transmembrane domain (˜residues 525-550),and a cytoplasmic domain (˜residues 551-574) at the C-terminus.

Three F₂-F₁ protomers oligomerize in the mature F protein, which adoptsa metastable “prefusion” conformation that is triggered to undergo aconformational change (to a “postfusion” conformation) upon contact witha target cell membrane. This conformational change exposes a hydrophobicsequence, known as the fusion peptide, which is located at theN-terminus of the F₁ polypeptide, and which associates with the hostcell membrane and promotes fusion of the membrane of the virus, or aninfected cell, with the target cell membrane.

A number of neutralizing antibodies that specifically bind to antigenicsites on RSV F protein have been identified. These include monoclonalantibodies 131-2a and 2F, which bind to antigenic site I (centeredaround residue P389); monoclonal antibodies palivizumab and motavizumab,which bind to antigenic site II (centered around residues 254-277); andmonoclonal antibodies 101F and mAb19, which bind to antigenic site IV(centered around residues 429-437).

Single chain RSV F protein: A recombinant RSV F protein that isexpressed as a single polypeptide chain including the RSV F₁ polypeptideand the RSV F₂ polypeptide. The single chain RSV F protein trimerizes toform a RSV F protein ectodomain. A single chain RSV F protein does notinclude the furin cleavage sites flanking the pep27 polypeptide of RSV Fprotein; therefore, when produced in cells, the F₀ polypeptide is notcleaved into separate F₁ and F₂ polypeptides. In some embodiments, asingle chain RSV F protein includes deletion of the two furin cleavagesites, the pep27 polypeptide, and the fusion peptide. In one embodiment,position 103 or 105 is linked to position 145 of the RSV protein togenerate the single chain construction. In several embodiments, theremaining portions of the F₁ and F₂ polypeptides are joined by a linker,such as a peptide linker.

RSV F₀ polypeptide (F₀): The precursor of the RSV F protein, includingthe amino acids of a N-terminal signal peptide, a F₂ polypeptide, apep27 polypeptide, and a F₁ polypeptide including the F₁ extracellulardomain, transmembrane domain and cytosolic tail. The native F₀polypeptide is proteolytically processed at a signal sequence cleavagesite, and two furin cleavage sites (approximately F₀ positions 109 and136; for example, RARR₁₀₉ (SEQ ID NO: 124, residues 106-109) and RKRR₁₃₆(SEQ ID NO: 124, residues 133-136), resulting in the F₁ and F₂fragments. Examples of F₀ polypeptides from many different RSV subgroupsare known, including from the A, B and bovine subgroups, examples ofwhich are set forth herein as SEQ ID NOs: 1-128, 129-177, and 178-184,respectively.

RSV F1 polypeptide (F₁): A peptide chain of the RSV F protein. As usedherein, “F₁ polypeptide” refers to both native F₁ polypeptides and F₁polypeptides including modifications (e.g., amino acid substitutions,insertions, or deletion) from the native sequence, for example,modifications designed to stabilize a recombinant F protein (includingthe modified F₁ polypeptide) in a RSV F protein prefusion conformation.Native F₁ includes approximately residues 137-574 of the RSV F₀precursor, and includes (from N- to C-terminus) an extracellular/lumenalregion (˜residues 137-524), a transmembrane domain (˜residues 525-550),and a cytoplasmic domain (˜residues 551-574). Several embodimentsinclude an F₁ polypeptide modified from a native F₁ sequence, forexample an F₁ polypeptide that lacks the transmembrane and cytosolicdomain, and/or includes one or more amino acid substitutions thatstabilize a recombinant F protein (containing the F₁ polypeptide) in aprefusion conformation. In one example, a disclosed RSV F proteinincludes a F₁ polypeptide with deletion of the transmembrane andcytosolic domains, and cysteine substitutions at positions 155 and 290.In another example, a disclosed RSV F protein includes a F₁ polypeptidewith deletion of the transmembrane and cytosolic domains, cysteinesubstitutions at positions 155 and 290, and a phenylalanine substitutionat position 190. In another example, a disclosed RSV F protein includesa F₁ polypeptide with deletion of the transmembrane and cytosolicdomains, cysteine substitutions at positions 155 and 290, aphenylalanine substitution at position 190, and a leucine substitutionat position 207. In several embodiments, the F1 polypeptide includes aC-terminal linkage to a trimerization domain. Many examples of native F₁sequences are known which are provided herein as approximately positions137-524 of SEQ ID NOs: 1-184.

RSV F₂ polypeptide (F2): A polypeptide chain of the RSV F protein. Asused herein, “F₂ polypeptide” refers to both native F₂ polypeptides andF₂ polypeptides including modifications (e.g., amino acid substitutions)from the native sequence, for example, modifications designed tostabilize a recombinant F protein (including the modified F₂polypeptide) in a RSV F protein prefusion conformation. Native F₂includes approximately residues 26-109 of the RSV F₀ precursor. Innative RSV F protein, the F₂ polypeptide is linked to the F₁ polypeptideby two disulfide bonds. Many examples of native F₂ sequences are knownwhich are provided herein as approximately positions 26-109 of SEQ IDNOs: 1-184.

RSV pep27 polypeptide (pep27): A 27 amino acid polypeptide that isexcised from the F₀ precursor during maturation of the RSV F protein.pep27 is flanked by two furin cleavage sites that are cleaved by acellular protease during F protein maturation to generate the F₁ and F₂polypeptide. Examples of native pep27 sequences are known which areprovided herein as positions 110-136 of SEQ ID NOs: 1-184.

RSV F protein prefusion conformation: A structural conformation adoptedby the RSV F protein prior to triggering of the fusogenic event thatleads to transition of RSV F to the postfusion conformation andfollowing processing into a mature RSV F protein in the secretorysystem. The three-dimensional structure of an exemplary RSV F protein ina prefusion conformation is disclosed herein (see Example 1) and thestructural coordinates of the exemplary RSV F protein in a prefusionconformation bound by the prefusion-specific antibody D25 are providedin Table 1. As shown herein, the prefusion conformation of RSV F issimilar in overall structure to the prefusion conformation of otherparamyxoviruses (such as PIV, see FIG. 7 ), though with some significantdifferences. In the prefusion state, the RSV F protein includes anantigenic site at the membrane distal apex (“antigenic site Ø,” seeExample 1), that includes RSV F residues 62-69 and 196-209, and alsoincludes the epitopes of the D25 and AM22 antibodies. As used herein, arecombinant RSV F protein stabilized in a prefusion conformation can bespecifically bound by an antibody that is specific for the prefusionconformation of the RSV F protein, such as an antibody that specificallybinds to an epitope within antigenic site Ø, for example, the D25 orAM22 antibody. Additional prefusion specific antibodies include the 5C4and MPE8 antibodies.

RSV F protein postfusion conformation: A structural conformation adoptedby the RSV F protein that is not the prefusion conformation, and inwhich the N- and C-termini of the RSV F protein are proximal in a stablecoil-coil. The post fusion conformation of RSV F protein has beendescribed at the atomic level (see, e.g., McLellan et al., J. Virol.,85, 7788, 2011; Swanson et al., Proc. Natl. Acad. Sci. U.S.A., 108,9619, 2011; and structural coordinates deposited PDB Accession No. 3RRR; each of which is incorporated by reference herein). The post-fusionconformation of RSV F protein is similar to that known for otherparamyxovirus glycoproteins, including the PIV5 F protein. In thepostfusion conformation, the RSV F protein does not include antigenicsite Ø, and therefore does not include the D25 epitope and is notspecifically bound by D25 or AM22. The RSV postfusion conformationoccurs, for example, following fusion of the F protein with the cellmembrane. The sequence of a RSV F protein that when expressed, can foldinto a post-fusion conformation, is provided as SEQ ID NO: 1469.

Resurfaced antigen or resurfaced immunogen: A polypeptide immunogenderived from a wild-type antigen in which amino acid residues outside orexterior to a target epitope are mutated in a systematic way to focusthe immunogenicity of the antigen to the selected target epitope. Insome examples a resurfaced antigen is referred to as anantigenically-cloaked immunogen or antigenically-cloaked antigen.

Root mean square deviation (RMSD): The square root of the arithmeticmean of the squares of the deviations from the mean. In severalembodiments, RMSD is used as a way of expressing deviation or variationfrom the structural coordinates of a reference three dimensionalstructure. This number is typically calculated after optimalsuperposition of two structures, as the square root of the mean squaredistances between equivalent C_(α) atoms. In some embodiments, thereference three-dimensional structure includes the structuralcoordinates of the RSV F protein bound to monoclonal antibody D25, setforth herein in Table 1.

Sequence identity/similarity: The identity/similarity between two ormore nucleic acid sequences, or two or more amino acid sequences, isexpressed in terms of the identity or similarity between the sequences.Sequence identity can be measured in terms of percentage identity; thehigher the percentage, the more identical the sequences are. Homologs ororthologs of nucleic acid or amino acid sequences possess a relativelyhigh degree of sequence identity/similarity when aligned using standardmethods.

Methods of alignment of sequences for comparison are well known in theart. Various programs and alignment algorithms are described in: Smith &Waterman, Adv. Appl. Math. 2:482, 1981; Needleman & Wunsch, J. Mol.Biol. 48:443, 1970; Pearson & Lipman, Proc. Natl. Acad. Sci. USA85:2444, 1988; Higgins & Sharp, Gene, 73:237-44, 1988; Higgins & Sharp,CABIOS 5:151-3, 1989; Corpet et al., Nuc. Acids Res. 16:10881-90, 1988;Huang et al. Computer Appls. in the Biosciences 8, 155-65, 1992; andPearson et al., Meth. Mol. Bio. 24:307-31, 1994. Altschul et al., J.Mol. Biol. 215:403-10, 1990, presents a detailed consideration ofsequence alignment methods and homology calculations.

Once aligned, the number of matches is determined by counting the numberof positions where an identical nucleotide or amino acid residue ispresent in both sequences. The percent sequence identity is determinedby dividing the number of matches either by the length of the sequenceset forth in the identified sequence, or by an articulated length (suchas 100 consecutive nucleotides or amino acid residues from a sequenceset forth in an identified sequence), followed by multiplying theresulting value by 100. For example, a peptide sequence that has 1166matches when aligned with a test sequence having 1554 amino acids is75.0 percent identical to the test sequence (1166 1554*100=75.0). Thepercent sequence identity value is rounded to the nearest tenth. Forexample, 75.11, 75.12, 75.13, and 75.14 are rounded down to 75.1, while75.15, 75.16, 75.17, 75.18, and 75.19 are rounded up to 75.2. The lengthvalue will always be an integer.

The NCBI Basic Local Alignment Search Tool (BLAST) (Altschul et al., J.Mol. Biol. 215:403, 1990) is available from several sources, includingthe National Center for Biotechnology Information (NCBI, Bethesda, MD)and on the internet, for use in connection with the sequence analysisprograms blastp, blastn, blastx, tblastn and tblastx. A description ofhow to determine sequence identity using this program is available onthe NCBI website on the internet.

Homologs and variants of a polypeptide are typically characterized bypossession of at least about 75%, for example at least about 80%, 85%,90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identitycounted over the full length alignment with the amino acid sequence ofinterest. Proteins with even greater similarity to the referencesequences will show increasing percentage identities when assessed bythis method, such as at least 80%, at least 85%, at least 90%, at least95%, at least 98%, or at least 99% sequence identity. When less than theentire sequence is being compared for sequence identity, homologs andvariants will typically possess at least 80% sequence identity overshort windows of 10-20 amino acids, and may possess sequence identitiesof at least 85% or at least 90% or 95% depending on their similarity tothe reference sequence. Methods for determining sequence identity oversuch short windows are available at the NCBI website on the internet.One of skill in the art will appreciate that these sequence identityranges are provided for guidance only; it is entirely possible thatstrongly significant homologs could be obtained that fall outside of theranges provided.

For sequence comparison of nucleic acid sequences, typically onesequence acts as a reference sequence, to which test sequences arecompared. When using a sequence comparison algorithm, test and referencesequences are entered into a computer, subsequence coordinates aredesignated, if necessary, and sequence algorithm program parameters aredesignated. Default program parameters are used. Methods of alignment ofsequences for comparison are well known in the art. Optimal alignment ofsequences for comparison can be conducted, e.g., by the local homologyalgorithm of Smith & Waterman, Adv. Appl. Math. 2:482, 1981, by thehomology alignment algorithm of Needleman & Wunsch, J. Mol. Biol.48:443, 1970, by the search for similarity method of Pearson & Lipman,Proc. Nat'l. Acad. Sci. USA 85:2444, 1988, by computerizedimplementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA inthe Wisconsin Genetics Software Package, Genetics Computer Group, 575Science Dr., Madison, WI), or by manual alignment and visual inspection(see, e.g., Sambrook et al. (Molecular Cloning: A Laboratory Manual,4^(th) ed, Cold Spring Harbor, New York, 2012) and Ausubel et al. (InCurrent Protocols in Molecular Biology, John Wiley & Sons, New York,through supplement 104, 2013). One example of a useful algorithm isPILEUP. PILEUP uses a simplification of the progressive alignment methodof Feng & Doolittle, J. Mol. Evol. 35:351-360, 1987. The method used issimilar to the method described by Higgins & Sharp, CABIOS 5:151-153,1989. Using PILEUP, a reference sequence is compared to other testsequences to determine the percent sequence identity relationship usingthe following parameters: default gap weight (3.00), default gap lengthweight (0.10), and weighted end gaps. PILEUP can be obtained from theGCG sequence analysis software package, e.g., version 7.0 (Devereaux etal., Nuc. Acids Res. 12:387-395, 1984.

Another example of algorithms that are suitable for determining percentsequence identity and sequence similarity are the BLAST and the BLAST2.0 algorithm, which are described in Altschul et al., J. Mol. Biol.215:403-410, 1990 and Altschul et al., Nucleic Acids Res. 25:3389-3402,1977. Software for performing BLAST analyses is publicly availablethrough the National Center for Biotechnology Information(ncbi.nlm.nih.gov). The BLASTN program (for nucleotide sequences) usesas defaults a word length (W) of 11, alignments (B) of 50, expectation(E) of 10, M=5, N=−4, and a comparison of both strands. The BLASTPprogram (for amino acid sequences) uses as defaults a word length (W) of3, and expectation (E) of 10, and the BLOSUM62 scoring matrix (seeHenikoff & Henikoff, Proc. Natl. Acad. Sci. USA 89:10915, 1989). Anoligonucleotide is a linear polynucleotide sequence of up to about 100nucleotide bases in length.

Another indicia of sequence similarity between two nucleic acids is theability to hybridize. The more similar are the sequences of the twonucleic acids, the more stringent the conditions at which they willhybridize. The stringency of hybridization conditions aresequence-dependent and are different under different environmentalparameters. Thus, hybridization conditions resulting in particulardegrees of stringency will vary depending upon the nature of thehybridization method of choice and the composition and length of thehybridizing nucleic acid sequences. Generally, the temperature ofhybridization and the ionic strength (especially the Na+ and/or Mg++concentration) of the hybridization buffer will determine the stringencyof hybridization, though wash times also influence stringency.Generally, stringent conditions are selected to be about 5° C. to 20° C.lower than the thermal melting point (T_(m)) for the specific sequenceat a defined ionic strength and pH. The T_(m) is the temperature (underdefined ionic strength and pH) at which 50% of the target sequencehybridizes to a perfectly matched probe. Conditions for nucleic acidhybridization and calculation of stringencies can be found, for example,in Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold SpringHarbor Laboratory Press, Cold Spring Harbor, N Y, 2001; Tijssen,Hybridization With Nucleic Acid Probes, Part I: Theory and Nucleic AcidPreparation, Laboratory Techniques in Biochemistry and MolecularBiology, Elsevier Science Ltd., NY, NY, 1993; and Ausubel et al. ShortProtocols in Molecular Biology, 4^(th) ed., John Wiley & Sons, Inc.,1999.

As used herein, reference to “at least 80% identity” refers to “at least80%, at least 85%, at least 90%, at least 91%, at least 92%, at least93%, at least 94%, at least 95%, at least 96%, at least 97%, at least98%, at least 99%, or even 100% identity” to a specified referencesequence.

Signal Peptide: A short amino acid sequence (e.g., approximately 18-25amino acids in length) that directs newly synthesized secretory ormembrane proteins to and through membranes (for example, the endoplasmicreticulum membrane). Signal peptides are typically located at theN-terminus of a polypeptide and are removed by signal peptidases afterthe polypeptide has crossed the membrane. Signal peptide sequencestypically contain three common structural features: an N-terminal polarbasic region (n-region), a hydrophobic core, and a hydrophilicc-region). Exemplary signal peptide sequences are set forth as residues1-25 of SEQ ID NOs: 1-182 (RSV F protein signal peptides from A, B, andbovine RSV).

Specifically bind: When referring to the formation of anantibody:antigen protein complex, refers to a binding reaction whichdetermines the presence of a target protein, peptide, or polysaccharide(for example a glycoprotein), in the presence of a heterogeneouspopulation of proteins and other biologics. Thus, under designatedconditions, an antibody binds preferentially to a particular targetprotein, peptide or polysaccharide (such as an antigen present on thesurface of a pathogen, for example RSV F) and does not bind in asignificant amount to other proteins or polysaccharides present in thesample or subject. An antibody that specifically binds to the prefusionconformation of RSV F protein (e.g., and antibody that specificallybinds to antigenic site Ø) does not specifically bind to the postfusionconformation of RSV F protein. Specific binding can be determined bymethods known in the art. With reference to an antibody:antigen orFab:antigen complex, specific binding of the antigen and antibody has aK_(d) (or apparent K_(d)) of less than about 10⁻⁶ Molar, such as lessthan about 10⁻⁷ Molar, 10⁻⁸ Molar, 10⁻⁹, or even less than about 10⁻¹⁰Molar.

Soluble protein: A protein capable of dissolving in aqueous liquid atroom temperature and remaining dissolved. The solubility of a proteinmay change depending on the concentration of the protein in thewater-based liquid, the buffering condition of the liquid, theconcentration of other solutes in the liquid, for example salt andprotein concentrations, and the heat of the liquid. In severalembodiments, a soluble protein is one that dissolves to a concentrationof at least 0.5 mg/ml in phosphate buffered saline (pH 7.4) at roomtemperature and remains dissolved for at least 48 hours.

Therapeutic agent: A chemical compound, small molecule, or othercomposition, such as nucleic acid molecule, capable of inducing adesired therapeutic or prophylactic effect when properly administered toa subject.

Therapeutically effective amount of effective amount: The amount ofagent, such as a disclosed antigen or immunogenic composition containinga disclosed antigen, that is sufficient to prevent, treat (includingprophylaxis), reduce and/or ameliorate the symptoms and/or underlyingcauses of any of a disorder or disease, for example to prevent, inhibit,and/or treat RSV infection. In some embodiments, a therapeuticallyeffective amount is sufficient to reduce or eliminate a symptom of adisease, such as RSV infection. For instance, this can be the amountnecessary to inhibit viral replication or to measurably alter outwardsymptoms of the viral infection. In general, this amount will besufficient to measurably inhibit virus (for example, RSV) replication orinfectivity. When administered to a subject, a dosage will generally beused that will achieve target tissue concentrations that has been shownto achieve in vitro inhibition of viral replication. It is understoodthat to obtain a protective immune response against a pathogen canrequire multiple administrations of the immunogenic composition. Thus, atherapeutically effective amount encompasses a fractional dose thatcontributes in combination with previous or subsequent administrationsto attaining a protective immune response.

Transmembrane domain: An amino acid sequence that inserts into a lipidbilayer, such as the lipid bilayer of a cell or virus or virus-likeparticle. A transmembrane domain can be used to anchor an antigen to amembrane. In some examples a transmembrane domain is a RSV F proteintransmembrane domain. Exemplary RSV F transmembrane domains are familiarto the person of ordinary skill in the art, and provided herein. Forexample, the amino acid sequences of exemplary RSV F transmembranedomains are provided as approximately positions 525-550 of SEQ ID NOs:1-183.

Transformed: A transformed cell is a cell into which a nucleic acidmolecule has been introduced by molecular biology techniques. As usedherein, the term transformation encompasses all techniques by which anucleic acid molecule might be introduced into such a cell, includingtransfection with viral vectors, transformation with plasmid vectors,and introduction of DNA by electroporation, lipofection, and particlegun acceleration.

Vaccine: A pharmaceutical composition that elicits a prophylactic ortherapeutic immune response in a subject. In some cases, the immuneresponse is a protective immune response. Typically, a vaccine elicitsan antigen-specific immune response to an antigen of a pathogen, forexample a viral pathogen, or to a cellular constituent correlated with apathological condition. A vaccine may include a polynucleotide (such asa nucleic acid encoding a disclosed antigen), a peptide or polypeptide(such as a disclosed antigen), a virus, a cell or one or more cellularconstituents.

Vector: A nucleic acid molecule as introduced into a host cell, therebyproducing a transformed host cell. Recombinant DNA vectors are vectorshaving recombinant DNA. A vector can include nucleic acid sequences thatpermit it to replicate in a host cell, such as an origin of replication.A vector can also include one or more selectable marker genes and othergenetic elements known in the art. Viral vectors are recombinant DNAvectors having at least some nucleic acid sequences derived from one ormore viruses.

A replication deficient viral vector that requires complementation ofone or more regions of the viral genome required for replication, as aresult of, for example a deficiency in at least onereplication-essential gene function. For example, such that the viralvector does not replicate in typical host cells, especially those in ahuman patient that could be infected by the viral vector in the courseof a therapeutic method. Examples of replication-deficient viral vectorsand systems for their use are known in the art and include; for examplereplication-deficient LCMV vectors (see, e.g., U.S. Pat. Pub. No.2010/0297172, incorporated by reference herein in its entirety) andreplication deficient adenoviral vectors (see, e.g., PCT App. Pub. No.WO2000/00628, incorporated by reference herein).

Virus: A virus consists essentially of a core of nucleic acid surroundedby a protein coat, and has the ability to replicate only inside a livingcell. “Viral replication” is the production of additional virus by theoccurrence of at least one viral life cycle. A virus may subvert thehost cells' normal functions, causing the cell to behave in a mannerdetermined by the virus. For example, a viral infection may result in acell producing a cytokine, or responding to a cytokine, when theuninfected cell does not normally do so. In some examples, a virus is apathogen.

Virus-like particle (VLP): A non-replicating, viral shell, derived fromany of several viruses. VLPs are generally composed of one or more viralproteins, such as, but not limited to, those proteins referred to ascapsid, coat, shell, surface and/or envelope proteins, orparticle-forming polypeptides derived from these proteins. VLPs can formspontaneously upon recombinant expression of the protein in anappropriate expression system. Methods for producing particular VLPs areknown in the art. The presence of VLPs following recombinant expressionof viral proteins can be detected using conventional techniques known inthe art, such as by electron microscopy, biophysical characterization,and the like. Further, VLPs can be isolated by known techniques, e.g.,density gradient centrifugation and identified by characteristic densitybanding. See, for example, Baker et al. (1991) Biophys. J. 60:1445-1456;and Hagensee et al. (1994) J. Virol. 68:4503-4505; Vincente, J InvertebrPathol., 2011; Schneider-Ohrum and Ross, Curr. Top. Microbiol. Immunol.,354: 53073, 2012).

II. DESCRIPTION OF SEVERAL EMBODIMENTS

It is disclosed herein that the RSV F protein undergoes a dramaticstructural rearrangement between its pre- and postfusion conformations(see Example 1, below). As shown in FIG. 2B, the N-terminal region ofthe F₁ polypeptide in the prefusion conformation (corresponding in partto the membrane distal lobe shown in FIG. 2A) includes the indicated α2,α3, β3, β4, and α4 helical and beta sheet structures, whereas thecorresponding region of the N-terminus of the F₁ polypeptide in thepostfusion structure includes an extended α5 helical structure. Further,the C-terminal region of the F₁ polypeptide in the prefusionconformation (corresponding in part to the membrane proximal lobe shownin FIG. 2A) includes the indicated β22, α9, and β23 beta sheet andhelical structures, whereas the corresponding C-terminal region of theof the F₁ polypeptide in the postfusion conformation structure includesan extended α10 helical structure. Thus, the membrane distal andmembrane proximal lobes of the RSV F protein in its prefusionconformation include several distinct structural elements that areabsent from the corresponding regions of the RSV F protein in itspostfusion conformation. Amino acid positions (and sequences)corresponding to these regions are highlighted in grey in FIG. 2 ,including positions 137-216, and 461-513 of the F₁ polypeptide.

RSV F protein antigens are provided that are stabilized or “locked” in aprefusion conformation, termed “PreF antigens.” Using structure-guideddesign, positions of the RSV F₁ and F₂ polypeptides are targeted formodification (e.g., amino acid substitution) to hinder or preventtransition of the RSV F protein from a pre- to postfusion conformation.Such antigens have utility, for example, as immunogens to induce aneutralizing response to RSV F protein.

A. Native RSVF Proteins

Native RSV F proteins from different RSV groups, as well as nucleic acidsequences encoding such proteins and methods, are known. For example,the sequence of several subtype A, B and bovine precursor RSV F₀proteins provided as SEQ ID NOs: 1-184. The GenInfo Identifier (gi) andcorresponding accession number for each of these sequences, as well asthe corresponding RSV group are provided in Table 3:

TABLE 3 Exemplary Subtype A, B and bovine RSV F protein sequences SEQ IDSubtype Accession 1 A >gi|113472470|gb|ABI35685.1 2A >gi|46405966|gb|AAS93651.1 3 A >gi|346682949|gb|AEO45830.1 4A >gi|392301680|gb|AFM55244.1 5 A >gi|392301896|gb|AFM55442.1 6A >gi|392301692|gb|AFM55255.1 7 A >gi|392301728|gb|AFM55288.1 8A >gi|392976459|gb|AFM95385.1 9 A >gi|392976475|gb|AFM95400.1 10A >gi|21689583|gb|AAM68157.1 11 A >gi|21689587|gb|AAM68160.1 12A >gi|346682981|gb|AEO45859.1 13 A >gi|352962949|gb|AEQ63444.1 14A >gi|353441614|gb|AEQ98752.1 15 A >gi|392301740|gb|AFM55299.1 16A >gi|346682971|gb|AEO45850.1 17 A >gi|346682992|gb|AEO45869.1 18A >gi|346683003|gb|AEO45879.1 19 A >gi|346683036|gb|AEO45909.1 20A >gi|21689579|gb|AAM68154.1 21 A >gi|326578296|gb|ADZ95777.1 22A >gi|330470871|gb|AEC32087.1 23 A >gi|346683058|gb|AEO45929.1 24A >gi|392301644|gb|AFM55211.1 25 A >gi|392301656|gb|AFM55222.1 26A >gi|392301776|gb|AFM55332.1 27 A >gi|46405962|gb|AAS93649.1 28A >gi|326578298|gb|ADZ95778.1 29 A >gi|392301872|gb|AFM55420.1 30A >gi|346682960|gb|AEO45840.1 31 A >gi|346683080|gb|AEO45949.1 32A >gi|227299|prf|1701388A/1-574 33 A >gi|352962996|gb|AEQ63487.1 34A >gi|352963032|gb|AEQ63520.1 35 A >gi|46405970|gb|AAS93653.1 36A >gi|392976437|gb|AFM95365.1 37 A >gi|392976449|gb|AFM95376.1 38A >gi|352962805|gb|AEQ63312.1 39 A >gi|346340362|gb|AEO23051.1 40A >gi|352962829|gb|AEQ63334.1 41 A >gi|352962865|gb|AEQ63367.1 42A >gi|392302028|gb|AFM55563.1 43 A >gi|392302016|gb|AFM55552.1 44A >gi|417346971|gb|AFX60137.1 45 A >gi|417347051|gb|AFX60173.1 46A >gi|392301812|gb|AFM55365.1 47 A >gi|29290039|gb|AAO72323.1 48A >gi|29290041|gb|AAO72324.1 49 A >gi|262479010|gb|ACY68435.1 50A >gi|330470867|gb|AEC32085.1 51 A >gi|392301704|gb|AFM55266.1 52A >gi|392301716|gb|AFM55277.1 53 A >gi|392301800|gb|AFM55354.1 54A >gi|345548062|gb|AEO12131.1 55 A >gi|346340367|gb|AEO23052.1 56A >gi|352962889|gb|AEQ63389.1 57 A >gi|353441606|gb|AEQ98748.1 58A >gi|353441604|gb|AEQ98747.1 59 A >gi|353441608|gb|AEQ98749.1 60A >gi|353441616|gb|AEQ98753.1 61 A >gi|353441620|gb|AEQ98755.1 62A >gi|353441624|gb|AEQ98757.1 63 A >gi|409905594|gb|AFV46409.1 64A >gi|409905610|gb|AFV46417.1 65 A >gi|417346953|gb|AFX60128.1 66A >gi|417347079|gb|AFX60187.1 67 A >gi|417346955|gb|AFX60129.1 68A >gi|417346967|gb|AFX60135.1 69 A >gi|417346979|gb|AFX60141.1 70A >gi|417346993|gb|AFX60148.1 71 A >gi|417346999|gb|AFX60151.1 72A >gi|417347043|gb|AFX60169.1 73 A >gi|417347105|gb|AFX60200.1 74A >gi|417347107|gb|AFX60201.1 75 A >gi|392301788|gb|AFM55343.1 76A >gi|409905578|gb|AFV46401.1 77 A >gi|409905596|gb|AFV46410.1 78A >gi|353441622|gb|AEQ98756.1 79 A >gi|409905582|gb|AFV46403.1 80A >gi|417347109|gb|AFX60202.1 81 A >gi|409905602|gb|AFV46413.1 82A >gi|409905604|gb|AFV46414.1 83 A >gi|417347121|gb|AFX60208.1 84A >gi|409905614|gb|AFV46419.1 85 A >gi|409905616|gb|AFV46420.1 86A >gi|417346973|gb|AFX60138.1 87 A >gi|417346997|gb|AFX60150.1 88A >gi|417347021|gb|AFX60162.1 89 A >gi|417347085|gb|AFX60190.1 90A >gi|425706126|gb|AFX95851.1 91 A >gi|392301836|gb|AFM55387.1 92A >gi|392301992|gb|AFM55530.1 93 A >gi|346683047|gb|AEO45919.1 94A >gi|46405974|gb|AAS93655.1 95 A >gi|46405976|gb|AAS93656.1 96A >gi|346683069|gb|AEO45939.1 97 A >gi|1353201|sp|P11209.2 98A >gi|1912295|gb|AAC57027.1 99 A >gi|9629375|ref|NP_044596.1 100A >gi|21263086|gb|AAM44851.1 101 A >gi|417346951|gb|AFX60127.1 102A >gi|417347009|gb|AFX60156.1 103 A >gi|29290043|gb|AAO72325.1 104A >gi|138252|sp|P12568.1 105 A >gi|226438|prf|1512372A 106A >gi|37674744|gb|AAQ97026.1 107 A >gi|37674754|gb|AAQ97031.1 108A >gi|37674746|gb|AAQ97027.1 109 A >gi|37674748|gb|AAQ97028.1 110A >gi|37674750|gb|AAQ97029.1 111 A >gi|37674752|gb|AAQ97030.1 112A >gi|146738079|gb|ABQ42594.1 113 A >gi|403379|emb|CAA81295.1 114A >gi|226838116|gb|ACO83302.1 115 A >gi|326578304|gb|ADZ95781.1 116A >gi|326578306|gb|ADZ95782.1 117 A >gi|326578308|gb|ADZ95783.1 118A >gi|326578310|gb|ADZ95784.1 119 A >gi|326578312|gb|ADZ95785.1 120A >gi|60549171|gb|AAX23994.1 121 A >gi|226838109|gb|ACO83297.1 122A >gi|352962877|gb|AEQ63378.1 123 A >gi|346683014|gb|AEO45889.1 124A >gi|138251|sp|P03420.1| 125 A >gi|1695263|gb|AAC55970.1 126A >gi|61211|emb|CAA26143.1 127 A >gi|226838114|gb|ACO83301.1 128A >gi|352963080|gb|AEQ63564.1 129 B >gi|109689536|dbj|BAE96918.1 130B >gi|380235900|gb|AFD34266.1 131 B >gi|401712638|gb|AFP99059.1 132B >gi|401712648|gb|AFP99064.1 133 B >gi|380235886|gb|AFD34259.1 134B >gi|326578302|gb|ADZ95780.1 135 B >gi|326578294|gb|ADZ95776.1 136B >gi|326578300|gb|ADZ95779.1 137 B >gi|380235892|gb|AFD34262.1 138B >gi|46405984|gb|AAS93660.1 139 B >gi|46405986|gb|AAS93661.1 140B >gi|46405990|gb|AAS93663.1 141 B >gi|46405992|gb|AAS93664.1 142B >gi|345121421|gb|AEN74946.1 143 B >gi|417347137|gb|AFX60215.1 144B >gi|380235888|gb|AFD34260.1 145 B >gi|346340378|gb|AEO23054.1 146B >gi|384872848|gb|AFI25262.1 147 B >gi|380235890|gb|AFD34261.1 148B >gi|46405978|gb|AAS93657.1 149 B >gi|46405982|gb|AAS93659.1 150B >gi|352963104|gb|AEQ63586.1 151 B >gi|352963128|gb|AEQ63608.1 152B >gi|352963164|gb|AEQ63641.1 153 B >gi|46405996|gb|AAS93666.1 154B >gi|417347131|gb|AFX60212.1 155 B >gi|417347135|gb|AFX60214.1 156B >gi|417347145|gb|AFX60219.1 157 B >gi|380235898|gb|AFD34265.1 158B >gi|352963116|gb|AEQ63597.1 159 B >gi|401712640|gb|AFP99060.1 160B >gi|352963152|gb|AEQ63630.1 161 B >gi|401712642|gb|AFP99061.1 162B >gi|417347133|gb|AFX60213.1 163 B >gi|417347147|gb|AFX60220.1 164B >gi|417347151|gb|AFX60222.1 165 B >gi|417347169|gb|AFX60231.1 166B >gi|417347171|gb|AFX60232.1 167 B >gi|417347175|gb|AFX60234.1 168B >gi|46405988|gb|AAS93662.1 169 B >gi|138250|sp|P13843.1 170B >gi|2582041|gb|AAB82446.1 171 B >gi|9629206|ref|NP_056863.1 172B >gi|38230490|gb|AAR14266.1 173 B >gi|326578292|gb|ADZ95775.1 174B >gi|345121416|gb|AEN74944.1 175 B >gi|345121418|gb|AEN74945.1 176B >gi|46405994|gb|AAS93665.1 177 B >gi|380235896|gb|AFD34264.1 178Bovine >gi|138247|sp|P22167.1 179 Bovine >gi|3451386|emb|CAA76980.1 180Bovine >gi|17939990|gb|AAL49399.1 181 Bovine >gi|9631275|ref|NP_048055.1182 Bovine >gi|94384139|emb|CAI96787.1 183Bovine >gi|425678|gb|AAB28458.1 184 Bovine >gi|17940002|gb|AAL49410.1

The RSV F protein exhibits remarkable sequence conservation across RSVsubtypes (see Table 3, which shows average pairwise sequence identityacross subtypes and F protein segments). For example, RSV subtypes A andB share 90% sequence identity, and RSV subtypes A and B each share 81%sequence identify with bRSV F protein, across the F₀ precursor molecule.Within RSV subtypes the F₀ sequence identity is even greater; forexample within each of RSV A, B, and bovine subtypes, the RSV F₀precursor protein has ˜98% sequence identity. Nearly all identified RSVF₀ precursor proteins are approximately 574 amino acids in length, withminor differences in length typically due to the length of theC-terminal cytoplasmic tail. Sequence identity across RSV F proteins isillustrated in Table 4:

TABLE 4 RSV F protein sequence identity hRSV A hRSV B bRSV (SEQ NOs:(SEQ NOs: (SEQ NOs: RSV subtype 1-128) 129-177) 178-184) F₀ (positions1-574) hRSV A 98% — — (SEQ NOs: 1-128) hRSV B 90% 99% — (SEQ NOs:129-177) Bovine RSV 81% 81% 98% (SEQ NOs: 178-184) F₂ (positions 26-109)hRSV A 98% — — (SEQ NO: 1-128) hRSV B 93% 99% — (SEQ NO: 129-177) BovineRSV 77% 77% 98% (SEQ NOs: 178-184) F₁ (positions 137-513) hRSV A 99% — —(SEQ NOs: 1-128) hRSV B 95% >99%  — (SEQ NOs: 129-177) Bovine RSV 91%92% 99% (SEQ NOs: 178-184)

In view of the conservation of RSV F sequences, the person of ordinaryskill in the art can easily compare amino acid positions betweendifferent native RSV F sequences, to identify corresponding RSV F aminoacid positions between different RSV strains and subtypes. For example,across nearly all identified native RSV F₀ precursor proteins, the furincleavage sites fall in the same amino acid positions. Thus, theconservation of RSV F protein sequences across strains and subtypesallows use of a reference RSV F sequence for comparison of amino acidsat particular positions in the RSV F protein. For the purposes of thisdisclosure (unless context indicates otherwise), RSV F protein aminoacid positions are given with reference to the reference F₀ proteinprecursor polypeptide set forth as SEQ ID NO: 124 (corresponding toGENBANK® Acc. No. P03420, incorporated by reference herein as present inGENBANK® on Feb. 28, 2013).

B. PreF Antigens

Isolated antigens are disclosed herein that include a recombinant RSV Fprotein stabilized in a prefusion conformation (“PreF antigens”). ThePreF antigens contain a recombinant RSV F protein or fragment thereofthat has been modified from a native form to increase immunogenicity.For example, the disclosed recombinant RSV F proteins have been modifiedfrom the native RSV sequence to be stabilized in a prefusionconformation. The person of ordinary skill in the art will appreciatethat the disclosed PreF antigens are useful to induce immunogenicresponses in vertebrate animals (such as mammals, for example, humansand cattle) to RSV (for example RSV A, RSV B, or bovine RSV). Thus, inseveral embodiments, the disclosed antigens are immunogens.

The D25 antibody recognizes a quaternary epitope including multipleprotomers of the RSV F protein. This epitope is contained within anantigenic site (“Antigenic site Ø”) located on the membrane-distal apexof the RSV F glycoprotein (see, e.g., FIG. 1C), when it is in aprefusion conformation. While the secondary structural elements of thethis epitope remains mostly unchanged between pre- and post-fusion Fconformations, their relative orientation changes substantially, withthe α4-helix pivoting ˜1800 relative to strand β2 in pre- andpost-fusion conformations (see, e.g., FIG. 3B). The conformationalchanges in the structure of the RSV F protein between the pre- andpost-fusion conformations determine the presence of the D25 epitope onthe RSV F protein. Accordingly, in several embodiments, a PreF antigenincluding a recombinant RSV F protein stabilized in a prefusionconformation can be identified by determining the specific binding ofthe D25 monoclonal antibody to the antigen. The person of ordinary skillin the art will appreciate that other antibodies that specifically bindto antigenic site Ø of the RSV F protein (such as the AM22 antibody or5C4 antibody), or other antibodies that are pre-fusion specific, but donot bind antigenic site Ø (such as MPE8) can also be used to identify aPreF antigen including a RSV F protein stabilized in a prefusionconformation.

Thus, the PreF antigens disclosed herein are specifically bound by anantibody that is specific for the RSV F prefusion conformation but notthe post-fusion conformation. In several embodiments, the PreF antigenis specifically bound by the D25 and/or AM22 antibody, which (asdisclosed herein) are antibodies specific for the pre- but notpost-fusion conformation of the RSV F protein. In several examples, theprefusion-specific antibody (such as D25 or AM22) specifically binds tothe PreF antigen with a dissociation constant of less than about 10⁻⁶Molar, such as less than about 10⁻⁷ Molar, 10⁻⁸ Molar, or less than 10⁻⁹Molar. Specific binding can be determined by methods known in the art.The determination of specific binding may readily be made by using oradapting routine procedures, such as ELISA, immunocompetition, surfaceplasmon resonance, or other immunosorbant assays (described in manystandard texts, including Harlow and Lane, Using Antibodies: ALaboratory Manual, CSHL, New York, 1999).

In further embodiments, the PreF antigen is not specifically bound by anantibody that binds the postfusion conformation of the RSV F protein.For example, an antibody specific for the six helix bundle found only inthe postfusion conformation of RSV F protein (e.g., as described inMagro et al., Proc. Nat'l. Acad. Sci. U.S.A., 109:3089-3094, 2012). Inseveral examples, the dissociation constant for the RSV F postfusionspecific antibody binding to the PreF antigen is greater than 10⁻⁵Molar, such as at least 10⁻⁵ Molar, 10⁻⁴ Molar, or 10⁻³.

In several embodiments, any of the PreF antigens includes a RSV Fprotein prefusion epitope (such as a D25 or AM22 epitope) in a RSV Fprotein prefusion-specific antibody-bound conformation (such as a D25 orAM22 bound conformation). For example, in several embodiments, any ofthe PreF antigens includes an epitope in a D25 or AM22 epitope-boundconfirmation (e.g., the conformation defined by the structuralcoordinates provided in Table 1) when the PreF antigen is not bound byD25 or AM22, that is, the PreF antigen is stabilized in the D25- orAM22-bound conformation. Methods of determining if a disclosed PreFantigen includes a RSV F protein prefusion epitope (such as a D25 orAM22 epitope) in a RSV F protein prefusion specific monoclonalantibody-bound conformation (such as a D25 or AM22 bound conformation)are known to the person of ordinary skill in the art and furtherdisclosed herein (see, for example, McLellan et al., Nature,480:336-343, 2011; and U.S. Patent Application Publication No.2010/0068217, each of which is incorporated by reference herein in itsentirety). For example, the disclosed three-dimensional structure of theD25 Fab fragment in complex with the RSV F protein can be compared withthree-dimensional structure of any of the disclosed PreF antigens.

The person of ordinary skill in the art will appreciate that a disclosedPreF antigen can include an epitope in a prefusion specific monoclonalantibody-bound conformation even though the structural coordinates ofantigen are not strictly identical to those of the prefusion F proteinas disclosed herein. For example, in several embodiments, any of thedisclosed PreF antigens include a RSV F prefusion-specific epitope (suchas a D25 or AM22 epitope) that in the absence of the RSV F prefusionspecific monoclonal antibody can be structurally superimposed onto thecorresponding epitope in complex with the RSV F prefusion specificmonoclonal antibody with a root mean square deviation (RMSD) of theircoordinates of less than 1.0, 0.75, 0.5, 0.45, 0.4, 0.35, 0.3 or 0.25Å/residue, wherein the RMSD is measured over the polypeptide backboneatoms N, Cα, C, O, for at least three consecutive amino acids.

In several embodiments, the PreF antigen is soluble in aqueous solution.For example, in some embodiments, the PreF antigen is soluble in asolution that lacks detergent. In some embodiments, the PreF antigendissolves to a concentration of at least 0.5 mg/ml (such as at least 1.0mg/ml, 1.5 mg/ml, 2.0 mg/ml, 3.0 mg/ml, 4.0 mg/ml or at least 5.0 mg/ml)in phosphate buffered saline (pH 7.4) at room temperature (e.g., 20-22degrees Celsius) and remains dissolved for at least for at least 12hours (such as at least 24 hours, at least 48 hours, at least one week,at least two weeks, or more time). In one embodiment, the phosphatebuffered saline includes NaCl (137 mM), KCl (2.7 mM), Na₂HPO₄ (10 mM),KH₂PO₄ (1.8 mM) at pH 7.4. In some embodiments, the phosphate bufferedsaline further includes CaCl₂ (1 mM) and MgCl₂ (0.5 mM). The person ofskill in the art is familiar with methods of determining if a proteinremains in solution over time. For example, the concentration of theprotein dissolved in a aqueous solution can be tested over time usingstandard methods.

In several embodiments, any of the disclosed PreF antigens can be usedto induce an immune response to RSV in a subject. In several suchembodiments, induction of the immune response includes production ofneutralizing antibodies to RSV. Methods to assay for neutralizationactivity are known to the person of ordinary skill in the art andfurther described herein, and include, but are not limited to, plaquereduction neutralization (PRNT) assays, microneutralization assays (seee.g., Anderson et al., J. Clin. Microbiol., 22: 1050-1052, 1985), orflow cytometry based assays (see, e.g., Chen et al., J. Immunol.Methods., 362:180-184, 2010). Additional neutralization assays aredescribed herein, and familiar to the person of ordinary skill in theart.

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein that, when dissolved in an aqueous solution, forms a populationof recombinant RSV F proteins stabilized in a prefusion conformation.The aqueous solution can be, for example, phosphate buffered saline atphysiological pH, such as pH 7.4. In some embodiments, the population isa homogeneous population including one or more recombinant RSV Fproteins that are, for example, all stabilized in a prefusionconformation. In some embodiments, at least about 90% of the recombinantRSV F proteins (such as at least about 91%, 92%, 93%, 94%, 95%, 96%,97%, 98%, 99% or 99.9% of the RSV F proteins) in the homogeneouspopulation are stabilized in the prefusion conformation. In someembodiments, at least about 90% of the recombinant RSV F proteins (suchas at least about 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 99.9%of the RSV F proteins) in the homogeneous population are specificallybound by a prefusion-specific antibody (e.g., D25 or AM22 antibody),and/or include a RSV F prefusion specific conformation (such asantigenic site Ø). It will be understood that a homogeneous populationof RSV F proteins in a particular conformation can include variations(such as protein modification variations, e.g., glycosylation state),that do not alter the conformational state of the RSV F protein. Inseveral embodiments, the population of recombinant RSV F protein remainshomogeneous over time. For example, the PreF antigen can include arecombinant RSV F protein that, when dissolved in aqueous solution,forms a population of recombinant RSV F proteins that is stabilized in aprefusion conformation for at least 12 hours, such as at least 24 hours,at least 48 hours, at least one week, at least two weeks, or more.

In several embodiments, the isolated PreF antigens are substantiallyseparated from RSV F proteins in a post-fusion conformation. Thus, thePreF antigen can be, for example, at least 80% isolated, at least 90%,95%, 98%, 99%, or even 99.9% separated from RSV F proteins in apostfusion conformation. In several embodiments, the PreF antigens arealso separated from RSV F proteins that do not include antigen site Øand/or are not specifically bound by a prefusion specific monoclonalantibody (such as D25 or AM22). For example, the PreF antigen can be atleast 80% isolated, at least 90%, 95%, 98%, 99%, or even 99.9% separatedfrom RSV F proteins that do not include antigen site Ø and/or are notspecifically bound by a prefusion specific monoclonal antibody (such asD25 or AM22).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein that, when incubated in an aqueous solution, forms a populationof recombinant RSV F proteins stabilized in a prefusion conformation,wherein at least 70% (such as at least 80%, or at least 90% or at least95% or at least 98%) of the isolated antigens in the populationspecifically bind to a RSV F protein prefusion-specific antibody (suchas D25 or AM22) after

-   -   (a) incubation for one hour in 350 mM NaCl pH 7.0, at 50° C.;    -   (b) incubation for one hour in 350 mM NaCl pH 3.5, at 25° C.;    -   (c) incubation for one hour in 350 mM NaCl pH 10, at 25° C.;    -   (d) incubation for one hour in 10 mM osmolarity, pH 7.0, at 25°        C.;    -   (e) incubation for one hour in 3000 mM osmolarity, pH 7.0, at        25° C.;    -   (g) a combination of two or more of (a)-(e); or    -   a combination of (a) and (b); (a) and (c); (a) and (d); (a) and        (e); (b) and (d); (b) and (e); (c) and (d); (c) and (e); (a),        (b), and (d); (a), (c), and (d); (a), (b), and (e); or (a), (c),        and (e)

In further embodiments, the PreF antigen includes a recombinant RSV Fprotein that, when incubated in an aqueous solution, forms a populationof recombinant RSV F proteins stabilized in a prefusion conformation,wherein at least 60% (such as at least 70%, at least 80%, or at least90%) of the isolated antigens in the population specifically bind to theprefusion-specific antibody after ten freeze-thaw cycles in 350 mM NaClpH 7.0.

In some embodiments, the PreF antigens are provided as a homogenouspopulation that does not include detectable RSV F protein in apost-fusion conformation. RSV F protein is detectable by negative stainelectron microscope and/or specific binding by a postfusion antibody.

1. Recombinant RSV F Proteins Stabilized in a Prefusion Conformation

The PreF antigens disclosed herein include a recombinant RSV F proteinstabilized in a prefusion conformation and include an F₁ polypeptide anda F₂ polypeptide. The F₁ polypeptide, F₂ polypeptide, or both, caninclude at least one modification (e.g., an amino acid substitution)that stabilizes the recombinant RSV F protein in its prefusionconformation. In several embodiments, the F₂ polypeptide and the F₁polypeptide are linked by a peptide linker (for example, in embodimentsincluding a single chain RSV F protein). Stabilization of therecombinant RSV F protein in the prefusion conformation preserves atleast one prefusion-specific epitope (i.e., an epitope present in thepre- (but not post-) fusion conformation of the RSV F protein) thatspecifically binds to a RSV F prefusion-specific monoclonal antibody(i.e., an antibody that specifically binds to the RSV F protein in aprefusion conformation, but not a post fusion conformation). Thus, thedisclosed PreF antigens are specifically bound by a prefusion-specificantibody (e.g., D25 or AM22 antibody), and/or includes a RSV F prefusionspecific conformation (such as antigenic site Ø).

In some examples, the PreF antigen includes a recombinant RSV F proteinincluding a F₁ and/or F₂ polypeptide from a RSV A virus, for example, aF₁ and/or F₂ polypeptide from a RSV F₀ protein provided as one of SEQ IDNOs: 1-128, or 370, that is modified to stabilize the recombinant RSV Fprotein in a prefusion conformation. In some examples, the PreF antigenincludes a recombinant RSV F protein including a F₁ and/or F₂polypeptide from a RSV B virus, for example, a F₁ and/or F₂ polypeptidefrom a RSV F₀ protein provided as one of SEQ ID NOs: 129-177, that ismodified to stabilize the recombinant RSV F protein in a prefusionconformation. In some examples, the PreF antigen includes a recombinantRSV F protein including a F₁ and/or F₂ polypeptide from a RSV bovinevirus, for example, a F₁ and/or F₂ polypeptide from a RSV F₀ proteinprovided as one of SEQ ID NOs: 178-184, that is modified to stabilizethe recombinant RSV F protein in a prefusion conformation. F₁ and/or F₂polypeptides from other RSV subtypes can also be used. The recombinantRSV F protein can include modifications of the native RSV sequences,such as amino acid substitutions, deletions or insertions, glycosylationand/or covalent linkage to unrelated proteins (e.g., a protein tag), aslong as the PreF antigen retains the recombinant RSV F proteinstabilized in a prefusion conformation. RSV F proteins from thedifferent RSV subgroups, as well as nucleic acid sequences encoding suchproteins and methods for the manipulation and insertion of such nucleicacid sequences into vectors, are disclosed herein and known in the art(see, e.g., Tan et al., PLOS one, 7: e51439, 2011; Sambrook et al.,Molecular Cloning, a Laboratory Manual, 2d edition, Cold Spring HarborPress, Cold Spring Harbor, N. Y. (1989); Ausubel et al., CurrentProtocols in Molecular Biology, Greene Publishing Associates and JohnWiley & Sons, New York, N. Y. (1994)).

In some embodiments, the recombinant RSV F protein comprises or consistsof a F₂ polypeptide and a F₁ polypeptide comprising amino acid sequencesat least 80% identical to amino acids 26-103 and 145-310, respectively,of a native RSV F protein sequence set forth as any one of SEQ ID NOs:1-184, such as SEQ ID NO: 124.

In some embodiments, the recombinant RSV F protein comprises or consistsof a F₂ polypeptide and a F₁ polypeptide comprising amino acid sequencesat least 80% (such as at least 90%, at least 95%, at least 98%, or even100%) identical to amino acids 26-103 and 145-513, respectively, of anative RSV F protein sequence set forth as any one of SEQ ID NOs: 1-184,such as SEQ ID NO: 124.

In some embodiments, the recombinant RSV F protein comprises or consistsof a F₂ polypeptide and a F₁ polypeptide comprising amino acid sequencesat least 80% (such as at least 90%, at least 95%, at least 98%, or even100%) identical to amino acids 26-103 and 145-529, respectively, of anative RSV F protein sequence set forth as any one of SEQ ID NOs: 1-184,such as SEQ ID NO: 124.

In some embodiments, the recombinant RSV F protein comprises or consistsof a F₂ polypeptide and a F₁ polypeptide comprising amino acid sequencesat least 80% (such as at least 90%, at least 95%, at least 98%, or even100%) identical to amino acids 26-103 and 145-551, respectively, of anative RSV F protein sequence set forth as any one of SEQ ID NOs: 1-184,such as SEQ ID NO: 124.

In some examples, the PreF antigen includes a recombinant RSV F proteinincluding a F₁ and/or F₂ polypeptide including a polypeptide sequenceshaving at least 75% (for example at least 85%, 90%, 95%, 96%, 97%, 98%or 99%) sequence identity with a RSV F₁ and/or F₂ polypeptide from a RSVA virus, for example, a F₁ and/or F₂ polypeptide from a RSV F₀ proteinprovided as one of SEQ ID NOs: 1-128 or 370. In further examples, thePreF antigen includes a recombinant RSV F protein including a F₁ and/orF₂ polypeptide including a polypeptide sequences having at least 75%(for example at least 85%, 90%, 95%, 96%, 97%, 98% or 99%) sequenceidentity with a RSV F₁ and/or F₂ polypeptide from a RSV B virus, forexample, a F₁ and/or F₂ polypeptide from a RSV F₀ protein provided asone of SEQ ID NOs: 129-177. In further examples, the PreF antigenincludes a recombinant RSV F protein including a F₁ and/or F₂polypeptide including a polypeptide sequences having at least 75% (forexample at least 85%, 90%, 95%, 96%, 97%, 98% or 99%) sequence identitywith a RSV F₁ and/or F₂ polypeptide from a RSV bovine virus, forexample, a F₁ and/or F₂ polypeptide from a RSV F₀ protein provided asone of SEQ ID NOs: 178-184.

In several embodiments, the PreF antigen includes a recombinant RSV Fprotein including a F₁ polypeptide including or consisting of at least300 consecutive amino acids (such as at least 310, 320, 330, 340, 350,360, 370, 380, 390, 400, 410, 420, or 430 consecutive amino acids) froma native F₁ polypeptide sequence, such as positions 137-513 of one ofSEQ ID NOs: 1-184 or 370, including any polypeptide sequences having atleast 75% (for example at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%,88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%) sequenceidentity to a native F₁ polypeptide sequence, such as positions 137-513of any one of SEQ ID NOs: 1-184 or 370. For example, in someembodiments, the PreF antigen includes a recombinant F protein includesa F₁ polypeptide including or consisting of positions 137-513, 137-481,137-491, or position 137 to the C-terminus, or positions 137- to thetransmembrane domain, of any one of SEQ ID NOs: 1-184 or 370, includingany polypeptide sequences having at least 75% (for example at least 85%,90%, 95%, 96%, 97%, 98% or 99%) sequence identity to a native F₁polypeptide sequence, such as positions 137-513, or position 137 to theC-terminus, or positions 137- to the transmembrane domain, any one ofSEQ ID NOs: 1-184 or 370. The person of ordinary skill in the art willappreciate that the PreF antigen including the recombinant RSV F proteincan include a F1 polypeptide with N- or C-terminal truncations (forexample, deletion of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35,40, 45, or 50 or more amino acids) compared to extracellular region of anative F1 polypeptide (for example, positions 137-524), as long as thePreF antigen is specifically bound by a prefusion-specific antibody(e.g., D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø).

In some embodiments, the PreF antigen includes a F₁ polypeptideincluding a maximum length, for example no more than 300, 310, 320, 330,340, 350, 360, 370, 380, 390, 400, 410, 420, 430, or no more than 440amino acids in length. The F₁ polypeptide may include, consist orconsist essentially of the disclosed sequences. The disclosed contiguousF₁ polypeptide sequences may also be joined at either end to otherunrelated sequences (for examiner, non-RSV F₁ protein sequences, non-RSVF protein sequences, non-RSV, non-viral envelope, or non-viral proteinsequences)

In several embodiments, the PreF antigen includes a recombinant RSV Fprotein including a F₂ polypeptide including or consisting of at least60 consecutive amino acids (such as at least 60, 61, 62, 63, 64, 65, 66,67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84,85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101,102, 103, 104, 105, 106, 107, 108 or 109 consecutive amino acids) from anative F₂ polypeptide sequence, such as positions 26-109 of any one ofSEQ ID NOs: 1-184 or 370, including a polypeptide sequences having atleast 75% (for example at least 85%, 90%, 95%, 96%, 97%, 98% or 99%)sequence identity to a native F₁ polypeptide sequence, such as positions26-109 any one of SEQ ID NOs: 1-184 or 370. For example, in someembodiments, the PreF antigen includes a recombinant F protein includinga F₂ polypeptide including or consisting of 70-109 consecutive aminoacids (such as 60-100, 75-95, 80-90, 75-85, 80-95, 81-89, 82-88, 83-87,83-84, or 84-85 consecutive amino acids) from a native F₂ polypeptidesequence, such as positions 26-109 any one of SEQ ID NOs: 1-184 or 370,including any polypeptide sequences having at least 75% (for example atleast 85%, 90%, 95%, 96%, 97%, 98% or 99%) sequence identity to a nativeF₂ polypeptide sequence, such as positions 137-513 any one of SEQ IDNOs: 1-184 or 370.

In some embodiments, the PreF antigen includes a F₂ polypeptide is alsoof a maximum length, for example no more than 60, 61, 62, 63, 64, 65,66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83,84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100amino acids in length. The F₂ polypeptide may include, consist orconsist essentially of the disclosed sequences. The disclosed contiguousF₂ polypeptide sequences may also be joined at either end to otherunrelated sequences (for examiner, non-RSV F₂ protein sequences, non-RSVF protein sequences, non-RSV, non-viral envelope, or non-viral proteinsequences).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including a F₂ polypeptide including or consisting of at least60 consecutive amino acids (such as at least 60, 61, 62, 63, 64, 65, 66,67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84,85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101,102, 103, 104, 105, 106, 107, 108 or 109 consecutive amino acids) from anative F₂ polypeptide sequence, such as positions 26-109 of any one ofSEQ ID NOs: 1-184 or 370, including polypeptide sequences having atleast 75% (for example at least 85%, 90%, 95%, 96%, 97%, 98% or 99%)sequence identity to a native F₂ polypeptide sequence, such as aminoacids 26-109 any one of SEQ ID NOs: 1-184 or 370, and further includes aF₁ polypeptide including or consisting of at least 300 consecutive aminoacids (such as at least 310, 320, 330, 340, 350, 360, 370, 380, 390,400, 410, 420, or 430 consecutive amino acids) from a native F₁polypeptide sequence, such as positions 137-513 of one of SEQ ID NOs:1-184 or 370, including any polypeptide sequences having at least 75%(for example at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%,90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%) sequence identity toa native F₁ polypeptide sequence, such as positions 137-513 of any oneof SEQ ID NOs: 1-184 or 370.

In one non-limiting example, the PreF antigen includes a recombinant RSVF protein including a F₂ polypeptide and a F₁ polypeptide includingpositions 26-109 and 137-513, respectively, of any one of SEQ ID NOs:1-184 or 370, including polypeptide sequences having at least 75% (forexample at least 85%, 90%, 95%, 96%, 97%, 98% or 99%) sequence identityto a positions 26-109 and 137-513, respectively, of any one of SEQ IDNOs: 1-184 or 370.

As noted above, the RSV F protein is initially synthesized as a F₀precursor protein and is cleaved at multiple sites (including twoconserved furin cleavage sites) during maturation in eukaryotic cells.Thus, the native RSV F protein lacks the N-terminal signal peptide andthe pep27 peptide (or a portion thereof) of the F₀ precursor protein. Inseveral embodiments, the disclosed recombinant RSV F proteins stabilizedin the prefusion conformation do not include the signal peptide (or aportion thereof) and/or do not include the pep27 peptide (or a portionthereof). The person of ordinary skill in the art will appreciate thatrecombinant RSV F proteins lacking the RSV F signal peptide and/or pep27peptide can be generated by expressing the recombinant F₀ polypeptide incells where the signal peptide and the pep27 peptide will be excisedfrom the F₀ precursor by cellular proteases.

Several embodiments include a PreF antigen including a multimer of anyof the disclosed recombinant RSV F proteins, for example, a multimerincluding 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more of the disclosedrecombinant RSV F proteins. In several examples, any of the disclosedrecombinant RSV F proteins can be linked (e.g., via a peptide linker) toanother of the recombinant RSV F proteins to form the multimer.

It is understood in the art that some variations can be made in theamino acid sequence of a protein without affecting the activity of theprotein. Such variations include insertion of amino acid residues,deletions of amino acid residues, and substitutions of amino acidresidues. These variations in sequence can be naturally occurringvariations or they can be engineered through the use of geneticengineering technique known to those skilled in the art. Examples ofsuch techniques are found in Sambrook J, Fritsch E F, Maniatis T et al.,in Molecular Cloning—A Laboratory Manual, 2nd Edition, Cold SpringHarbor Laboratory Press, 1989, pp. 9.31-9.57), or in Current Protocolsin Molecular Biology, John Wiley & Sons, N.Y. (1989), 6.3.1-6.3.6, bothof which are incorporated herein by reference in their entirety. Thus,in some embodiments, the PreF antigen includes a F₁ polypeptide, a F₂polypeptide, or both a F₁ and F₂ polypeptide, that include one or moreamino acid substitutions compared to the corresponding native RSVsequence. For example, in some embodiments, the F₁ polypeptide, F₂polypeptide, or both the F₁ polypeptide and the F₂ polypeptide, includeup to 20 (such as up to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, or 19) amino acid substitutions compared to a native F₁polypeptide sequence, such as a native RSV sequence set forth as any oneof SEQ ID NOs: 1-184 or 370, wherein the PreF antigen is specificallybound by a RSV F prefusion-specific antibody (e.g., D25 or AM22antibody), and/or includes a RSV F prefusion specific conformation (suchas antigenic site Ø). In additional embodiments, the F₁ polypeptide, F₂polypeptide, or both the F₁ polypeptide and the F₂ polypeptide, includeup to 20 (such as up to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, or 19) conservative amino acid substitutions compared toa native F₁ polypeptide sequence, such as a native RSV sequence setforth as any one of SEQ ID NOs: 1-184 or 370, wherein the PreF antigenis specifically bound by a RSV F prefusion-specific antibody (e.g., D25or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø). For example, in someembodiments, the PreF antigen includes a recombinant RSV F protein in aprefusion conformation that is modified to increase expression of theprotein for protein productions purposes, e.g., by elimination of one ormore nuclear localization signals present on the RSV F protein.Manipulation of the nucleotide sequence encoding the F₁ or F₂polypeptide sequence (such as a nucleotide sequence encoding the F₀polypeptide including the F₁ and F₂ polypeptides) using standardprocedures, including in one specific, non-limiting, embodiment,site-directed mutagenesis or in another specific, non-limiting,embodiment, PCR, can be used to produce such variants. Alternatively,the F₁ and F₂ polypeptides can be synthesized using standard methods.The simplest modifications involve the substitution of one or more aminoacids for amino acids having similar biochemical properties. Theseso-called conservative substitutions are likely to have minimal impacton the activity of the resultant protein.

a. Membrane Distal Stabilizing Modifications

As disclosed herein, the RSV F protein undergoes a structuralrearrangement between its pre- and post-fusion conformations. As shownin FIG. 2B, the N-terminal region of the F₁ polypeptide in the prefusionconformation (corresponding in part to the membrane distal lobe shown inFIG. 2A) includes the indicated α2, 03, 03, 4, and α4 helical and betasheet structures, whereas the corresponding region of the N-terminus ofthe F₁ polypeptide in the postfusion structure includes an extended α5helical structure—the α2, α3, β3, β4, and α4 helical and beta sheetstructures are absent. Further, the C-terminal region of the F₁polypeptide in the prefusion conformation (corresponding in part to themembrane proximal lobe shown in FIG. 2A) includes the indicated β22, α9,and β23 beta sheet and helical structures, whereas the correspondingC-terminal region of the F₁ polypeptide in the postfusion conformationstructure includes an extended α10 helical structure and extendedcoil—the β22, α9, and β23 beta sheet and helical structures are absent.Thus, the membrane distal and membrane proximal lobes of the RSV Fprotein in its prefusion conformation include several distinctstructural elements that are absent from the corresponding regions ofthe RSV F protein in its postfusion conformation.

Guided by the structural features identified in the pre- and post-fusionconformations of the RSV F protein, several modes of stabilizing the RSVF protein in a prefusion conformation are available, including aminoacid substitutions that introduce one or more non-natural disulfidebonds, fill cavities within the RSV F protein, alter the packing ofresidues in the RSV F protein, introduce N-linked glycosylation sites,and combinations thereof. The stabilize modifications provided hereinare targeted modifications that stabilize the recombinant RSV F proteinin the prefusion conformation. In several embodiments, the RSV F proteinis not stabilized by non-specific cross-linking, such as glutaraldehydecrosslinking, for example glutaraldehyde crosslinking of membrane boundRSV F trimers.

In some non-limiting embodiments, the PreF antigen includes arecombinant RSV F protein stabilized in a prefusion conformation byintroduction of a disulfide bond, wherein the recombinant RSV F proteinincludes S155C and S290C; G151C and I288C; A153C and K461C; A149C andY458C; G143C and S404S substitutions; or Y33C and V469C amino acidsubstitutions. Non-limiting examples of precursor proteins of suchrecombinant RSV F proteins (including a Foldon domain linked to theC-terminus of the F1 polypeptide) are set forth herein as SEQ ID NO:185, SEQ ID NO: 189, SEQ ID NO: 205, SEQ ID NO: 207, SEQ ID NO: 209, andSEQ ID NO: 211. In further non-limiting embodiments, the PreF antigenincludes a recombinant RSV F protein stabilized in a prefusionconformation by introduction of a disulfide bond and one or more cavityfilling substitutions, wherein the recombinant RSV F protein includesS155C, S290C substitutions, and a large hydrophobic residue at position190, and/or position 207 (e.g., a S190F, S190W, or S190L substation,and/or a V207L, V207F, or V207W substitution). Non-limiting examples ofprecursor proteins of such recombinant RSV F precursor proteins(including a foldon domain linked to the C-terminus of the F1polypeptide) are set forth herein as SEQ ID NO: 371, SEQ ID NO: 372, SEQID NO: 373, SEQ ID NO: 374, SEQ ID NO: 375, and SEQ ID NO: 376.

Many of the sequences of recombinant RSV F proteins disclosed hereininclude the sequence of protease cleavage sites (such as thrombinsites), protein tags (such as a His tag, a Strep Tag II, a Avi tag,etc., that are not essential for the function of the RSV F protein, suchas for induction of an immune response in a subject. The person ofordinary skill in the art will recognize such sequences, and whenappropriate, understand that these tags or protease cleavage sites arenot included in a disclosed recombinant RSV F protein.

i. Non-natural Disulfide Bonds

In several embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a prefusion conformation by at least onenon-natural disulfide bond including a pair of cross-linked cysteineresidues. A non-natural disulfide bond is one that does not occur in anative RSV F protein, and is introduced by protein engineering (e.g., byincluding one or more substituted cysteine residues that form thenon-natural disulfide bond). For example, in some embodiments, any ofthe disclosed recombinant RSV F protein is stabilized in a prefusionconformation by any one of 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 disulfidebonds including a pair of cross-linked cysteine residues. In onespecific non-limiting example, the recombinant RSV F protein isstabilized in a prefusion conformation by a single pair of cross-linkedcysteine residues. In another non-limiting example, any of the disclosedrecombinant RSV F protein is stabilized in a prefusion conformation bytwo pairs of crosslinked cysteine residues.

The cysteine residues that form the disulfide bond can be introducedinto native RSV F protein sequence by one or more amino acidsubstitutions. For example, in some embodiments, a single amino acidsubstitution introduces a cysteine that forms a disulfide bond with acysteine residue present in the native RSV F protein sequence. Inadditional embodiments, two cysteine residues are introduced into anative RSV sequence to form the disulfide bond. The location of thecysteine (or cysteines) of a disulfide bond to stabilize the RSV Fprotein in a prefusion conformation can readily be determined by theperson of ordinary skill in the art using the disclosed structure of RSVF protein in its prefusion conformation, and the previously identifiedstructure of RSV F protein in its post fusion conformation.

For example, the amino acid positions of the cysteines are typicallywithin a sufficiently close distance for formation of a disulfide bondin the prefusion conformation of the RSV F protein. Methods of usingthree-dimensional structure data to determine if two residues are withina sufficiently close distance to one another for disulfide bondformation are known (see, e.g., Peterson et al., Protein engineering,12:535-548, 1999 and Dombkowski, Bioinformatics, 19:1852-1853, 3002(disclosing DISULFIDE BY DESIGN™), each of which is incorporated byreference herein). For example, residues can be selected manually, basedon the three dimensional structure of RSV F protein in a prefusionconformation provided herein, or a software, such as DISULFIDEBYDESIGN™,can be used. Without being bound by theory, ideal distances forformation of a disulfide bond are generally considered to be about −5.6Å for Cα-Cα distance, ˜2.02 Å for Sγ-Sγ distance, and 3.5-4.25 Å forCβ-Cβ distance (using the optimal rotomer). The person of ordinary skillin the art will appreciate that variations from these distances areincluded when selecting residues in a three dimensional structure thatcan be substituted for cysteines for introduction of a disulfide bond.For example, in some embodiments the selected residues have a Cα-Cαdistance of less than 7.0 Å and/or a Cβ-Cβ distance of less than 4.7 Å.In some embodiments the selected residues have a Cα-Cα distance of from2.0-8.0 Å and/or a Cβ-Cβ distance of from 2.0-5.5 Å. In severalembodiments, the amino acid positions of the cysteines are within asufficiently close distance for formation of a disulfide bond in theprefusion, but not post-fusion, conformation of the RSV F protein.

The person of ordinary skill in the art can readily determine therelative position of a particular amino acid between the pre- andpost-fusion conformations of the RSV F protein, for example by comparingthe prefusion structures defined herein by the structural coordinatesprovided in Table 1, with the previously identified postfusion structuredescribed in McLellan et al., J. Virol., 85, 7788, 2011, with structuralcoordinates deposited as PDB Accession No. 3 RRR). Methods ofdetermining relative position of a particular amino acid between the twoprotein structures (e.g., between the three dimensional structures pre-and post-fusion RSV F protein) are known. For example the person ofordinary skill in the art can use known superimposition methods tocompare the two structures (e.g., methods using the LSQKAB program(Kabsch W. Acta. Cryst. A 32 922-923 (1976)). In one example, the pre-and postfusion structures can be superimposed by using LSQKAB to align Fprotein positions 26-60, 77-97, 220-322, and 332-459 defined by thestructural coordinates provided in Table 1, with the F protein positions26-60, 77-97, 220-322, and 332-459 defined by the structural coordinatesdeposited as PDB Accession No. 3 RRR, and comparing the distance betweenthe Cα atom for each residue in the pre- and post-fusion structures toidentify the deviation of particular residues between the twostructures.

In several embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a prefusion conformation by a disulfide bondbetween a cysteine introduced into an amino acid position that changesconformation, and a cysteine introduced into an amino acid position thatdoes not change conformation, between the pre- and post-fusionstructures, respectively. For example, in some embodiments, the PreFantigen includes a recombinant RSV F protein including amino acidsubstitutions introducing a pair of cysteines, wherein the firstcysteine is in an amino acid position of the RSV F protein that has aroot mean square deviation of at least 5 (such as at least 6, at least7, at least 8, at least 9 or at least 10) angstroms between thethree-dimensional structure of the RSV F protein pre- and post-fusionconformations, and the second cysteine is in an amino acid position ofthe RSV F protein that has a root mean square deviation of less than 4(such as less than 3, 2, or 1) angstroms between the three-dimensionalstructure of the RSV F protein pre- and post-fusion conformations,wherein the PreF antigen is specifically bound by a prefusion-specificantibody (e.g., D25 or AM22 antibody), and/or includes a RSV F prefusionspecific conformation (such as antigenic site Ø).

Based on a comparison of the pre- and post-fusion RSV F structures,there are at least two regions that undergo large conformationalchanges, located at the N- and C-termini of the F₁ subunit (residues137-216 and 461-513, respectively). For example, as illustrated in FIG.2B, the positions 137-216 and 461-513 of the F₁ polypeptide undergostructural rearrangement between the Pre- and Post-F proteinconformations, whereas positions 217-460 of the F₁ polypeptide remainrelatively unchanged. Thus, in some embodiments, the PreF antigenincludes a recombinant RSV F protein stabilized in a prefusionconformation by a disulfide bond between a first cysteine in one ofpositions 137-216 or 461-513 of the F₁ polypeptide, and a secondcysteine in one of positions 217-460 of the F₁ polypeptide. In furtherembodiments, the PreF antigen includes a recombinant RSV F proteinstabilized in a prefusion conformation by a disulfide bond between afirst cysteine in one of positions 137-216 or 461-513 of the F₁polypeptide, and a second cysteine in a position of the F2 polypeptide,such as one of positions 26-109 (for example, one of positions 26-61 or77-97) of the F₂ polypeptide.

In additional embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a prefusion conformation by a disulfide bondbetween cysteines that are introduced into amino acid positions thatchange conformation between the pre- and post-fusion structures,respectively. For example, in some embodiments, the PreF antigenincludes a recombinant RSV F protein including amino acid substitutionsintroducing a pair of cysteines, wherein the first cysteine and thesecond cysteine is in an amino acid position of the RSV F protein thathas a root mean square deviation of at least 5 (such as at least 6, atleast 7, at least 8, at least 9 or at least 10) angstroms between thethree-dimensional structure of the RSV F protein pre- and post-fusionconformations, wherein the PreF antigen includes specific bindingactivity to an RSV F prefusion-specific antibody (e.g., D25 or AM22antibody), and/or includes a RSV F prefusion specific epitope (e.g., aD25 or AM22 epitope). In some such embodiments, the PreF antigenincludes a recombinant RSV F protein stabilized in a prefusionconformation by a disulfide bond between a the first cysteine and thesecond cysteine in positions 137-216 of the F₁ polypeptide. Inadditional embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a prefusion conformation by a disulfide bondbetween the first cysteine and the second cysteine in positions 461-513of the F₁ polypeptide. In further embodiments, the PreF antigen includesa recombinant RSV F protein stabilized in a prefusion conformation by adisulfide bond between the first cysteine and the second cysteine inpositions 137-216 and 461-513, respectively, of the F₁ polypeptide.

The person of ordinary skill in the art can readily determine thelocation of a particular amino acid in the pre- and post-fusionconformations of the RSV F protein (and any difference in a positionbetween the two conformations) using the structural coordinates of thethree-dimensional structure the RSV F protein in the prefusionconformation (which are set forth in Table 1), and the structuralcoordinates of the three-dimensional structure of the RSV F protein inthe postfusion conformation (which are set forth in Protein DatabankAccession No. 3 RRR). For example, such comparison methods are describedin Example 1. Table 5 provides examples of cysteine pairs and amino acidsubstitutions that can be used to stabilize a RSV F protein in aprefusion conformation.

TABLE 5 Exemplary Cysteine Pairs for Disulfide Bond StabilizationSubstitutions corresponding SEQ ID F protein Residue Pair(s) forCysteine Substitution to SEQ ID NO: 124 NO F₁ substitutions -Intra-Protomer Disulfide Bond 1 155 and 290 S155C and S290C 185 2 151and 288 G151C and I288C 189 3 137 and 337 F137C and T337C 213 4 397 and487 T397C and E487C 247 5 138 and 353 L138C and P353C 257 6 341 and 352W341C and F352C 267 7 403 and 420 S403C and T420C 268 8 319 and 413S319C and I413C 269 9 401 and 417 D401C and Y417C 270 10 381 and 388L381C and N388C 271 11 320 and 415 P320C and S415C 272 12 319 and 415S319C and S415C 273 13 331 and 401 N331C and D401C 274 14 320 and 335P320C and T335C 275 15 406 and 413 V406C and I413C 277 16 381 and 391L381C and Y391C 278 17 357 and 371 T357C and N371C 279 18 403 and 417S403C and Y417C 280 19 321 and 334 L321C and L334C 281 20 338 and 394D338C and K394C 282 21 288 and 300 I288C and V300C 284 F₂ and F₁Substitutions - Intra-Protomer Disulfide Bond 22 60 and 194 E60C andD194C 190 23 33 and 469 Y33C and V469C 211 24 54 and 154 T54C and V154C212 25 59 and 192 I59C and V192C 246 26 46 and 311 S46C and T311C 276 2748 and 308 L48C and V308C 283 28 30 and 410 E30C and L410C 285 F₁substitutions - Inter-Protomer Disulfide Bond 29 400 and 489 T400C andD489C 201 30 144 and 406 V144C and V406C 202 31 153 and 461 A153C andK461C 205 32 149 and 458 A149C and Y458C 207 33 143 and 404 G143C andS404S 209 34 346 and 454 S346C and N454C 244 35 399 and 494 K399C andQ494C 245 36 146 and 407 S146C and I407C 264 37 374 and 454 T374C andN454C 265 38 369 and 455 T369C and T455C 266 39 402 and 141 V402C andL141C 302 F₂ and F₁ Substitutions - Inter-Protomer Disulfide Bond 40 74and 218 A74C and E218C 243 Amino acid insertions to orient the Disulfidebond 41 145 and 460 (Inter), AA insertion between S145C and 460C; AAinsertion between 338 positions 146 and 147 positions 146/147 42 183 and423 (Inter), AAA insertion between N183C and K423C; AAA insertionbetween 339 positions 182 and 183 positions 182/183 43 330 and 430(Inter); CAA insertion between A329C and S430C; and a CAA insertion 340positions 329 and 330 between positions 329 and 330 Combinations 44 155and 290 (Intra); and 402 and 141 (Inter) S155C and S290C; and V402C andL141C 303 45 155 and 290(Intra); and 74 and 218 S155C and S290C; andA74C and E218C 263 46 155 and 290 (Intra); and 146 and 460 (Inter); GS155C and S290C; and S146C and N460C; G 258 insertion between position460 and 461 insertion between position 460 and 461 47 155 and 290(Intra); and 345 and 454(Inter); C S155C and S290C; and N345C and N454G;C 259 insertion between positions 453 and 454 insertion betweenpositions 453 and 454 48 155 and 290 (Intra); and 374 and 454(Inter); CS155C and S290C; and T374C and N454G; C 260 insertion between positions453 and 454 insertion between positions 453 and 454 49 155 and 290(Intra); and 239 and 279(Inter); C S155C and S290C; and S238G and Q279C;C 261 insertion between positions 238 and 239 insertion betweenpositions 238 and 239 50 155 and 290 (Intra); and 493 paired with CS155C and S290C; and S493C paired with a 262 insertion between positions329 and 330 C insertion between positions 329 and 330 51 183 and 428(Inter), G insertion between N183C and N428C; G insertion between 296positions 182 and 183 positions 182 and 183 52 183 and 428 (Inter), Cinsertion between N183C and N427G; C insertion between 297 positions 427and 428 positions 427 and 428 53 155 and 290 (Intra); and 183 and428(Inter); G S155C and S290C; and N183C and N428C; G 298 insertionbetween positions 182 and 183 insertion between positions 182 and 183 54155 and 290 (Intra); and 183 and 428(Inter); C S155C and S290C; andN183C and N427G; C 299 insertion between positions 427 and 428 insertionbetween positions 427 and 428

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including one or more (such as 2, 3, 4, 5, 6, 7, 8, 9 or 10)disulfide bonds, including disulfide bond between cysteine residueslocated at the RSV F positions listed in one or more of rows 1, 2, 3, 4,5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41,42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, or 54 of column 2 ofTable 5, wherein the PreF antigen is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ).

In further embodiments, the PreF antigen includes a recombinant RSV Fprotein including one or more (such as 2, 3, 4, 5, 6, 7, 8, 9 or 10)disulfide bonds, including disulfide bonds between cysteine residuesthat are introduced by the cysteine amino acid substitutions listed inone or more of rows 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,52, 53, or 54 of column 3 of Table 5, wherein the PreF antigen isspecifically bound by a prefusion-specific antibody (e.g., D25 or AM22antibody), and/or includes a RSV F prefusion specific conformation (suchas antigenic site Ø).

The SEQ ID NOs listed in column 4 of Table 5 set forth amino acidsequences including the indicated substitutions, as well as, a signalpeptide, F₂ polypeptide (positions 26-109), a pep27 polypeptide(positions 110-136), a F₁ polypeptide (positions 137-513), atrimerization domain (a Foldon domain) and a thrombin cleavage site(LVPRGS (positions 547-552 of SEQ ID NO: 185)) and purification tags(his-tag (HHHHHH (positions 553-558 of SEQ ID NO: 185)) and Strep Tag II(SAWSHPQFEK (positions 559-568 of SEQ ID NO: 185))).

Thus, in additional embodiments, the PreF antigen includes a RSV Fprotein including a F₁ polypeptide and a F₂ polypeptide as set forth inany one of the SEQ ID NOs listed in column 4 of Table 5, such as a SEQID NO listed in one of rows 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49,50, 51, 52, 53, or 54 of column 4 of Table 5, wherein the PreF antigenis specifically bound by a prefusion-specific antibody (e.g., D25 orAM22 antibody), and/or includes a RSV F prefusion specific conformation(such as antigenic site Ø). For example, the PreF antigen can include aRSV F protein including a F₁ polypeptide and a F₂ polypeptide, whereinthe F₂ and the F₁ polypeptide include the amino acid sequence set forthas positions 26-109 and 137-513, respectively, of any one of the SEQ IDNOs listed in column 4 of Table 5, such as a SEQ ID NO listed in one ofrows 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37,38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, or 54 ofcolumn 4 of Table 5, wherein the PreF antigen is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ).

In further embodiments, the PreF antigen includes a recombinant RSV Fprotein including one or more (such as 2, 3, 4, 5, 6, 7, 8, 9 or 10)intra-protomer disulfide bonds, including disulfide bond betweencysteine residues located at the RSV F positions of the F₁ polypeptidelisted in of one or more of rows 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,13, 14, 15, 16, 17, 18, 19, 20, or 21 of column 2 Table 5. For example,the PreF antigen can include a recombinant RSV F protein including oneor more (such as 2, 3, 4, 5, 6, 7, 8, 9 or 10) intra-protomer disulfidebonds, including disulfide bonds between cysteine residues that areintroduced by the F₁ polypeptide amino acid substitutions listed in ofone or more of rows 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,16, 17, 18, 19, 20, or 21 of column 3 of Table 5. In any of theseembodiments, the PreF antigen is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ).

In further embodiments, the PreF antigen includes a recombinant RSV Fprotein including one or more (such as 2, 3, 4, 5, 6, or 7)intra-protomer disulfide bonds, including disulfide bond betweencysteine residues located at the RSV F positions of the F₂ and F₁polypeptides listed in of one or more of rows 22, 23, 24, 25, 26, 27, or28 of column 2 of Table 5. For example, the PreF antigen can include arecombinant RSV F protein including one or more (such as 2, 3, 4, 5, 6,or 7) intra-protomer disulfide bonds, including disulfide bond betweencysteine residues that are introduced by the F₂ and F₁ polypeptide aminoacid substitutions listed in of one or more of rows 22, 23, 24, 25, 26,27, or 28 of column 3 of Table 5. In any of these embodiments, the PreFantigen is specifically bound by a prefusion-specific antibody (e.g.,D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø).

In further embodiments, the PreF antigen includes a recombinant RSV Fprotein including one or more (such as 2, 3, 4, 5, 6, 7, 8, 9 or 10)inter-protomer disulfide bonds, including disulfide bond betweencysteine residues located at the RSV F positions of the F₁ polypeptidelisted in one or more of rows 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, or39 of column 2 of Table 5. For example, the PreF antigen can include arecombinant RSV F protein including one or more (such as 2, 3, 4, 5, 6,7, 8, 9 or 10) inter-protomer disulfide bonds, including disulfide bondbetween cysteine residues that are introduced by the F₁ polypeptideamino acid substitutions listed in of one or more of rows 29, 30, 31,32, 33, 34, 35, 36, 37, 38, or 39 of column 3 of Table 5. In any ofthese embodiments, the PreF antigen is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ).

In further embodiments, the PreF antigen includes a recombinant RSV Fprotein including an inter-protomer disulfide bond between cysteineresidues located at the RSV F positions of the F₂ and F₁ polypeptideslisted in column 2 of row 40 of Table 5. In further embodiments, thePreF antigen includes a recombinant RSV F protein including aninter-protomer disulfide bond between cysteine residues that areintroduced by the amino acid substitutions in the F₂ and F₁ polypeptidelisted in column 3 of row 40 of Table 5. In any of these embodiments,the PreF antigen is specifically bound by a prefusion-specific antibody(e.g., D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø).

In some embodiments, amino acids can be inserted (or deleted) from the Fprotein sequence to adjust the alignment of residues in the F proteinstructure, such that particular residue pairs are within a sufficientlyclose distance to form an intra- or inter-protomer disulfide bond in theprefusion, but not postfusion, conformation. In several suchembodiments, the PreF antigen includes a recombinant RSV F proteinincluding a disulfide bond between cysteine residues located at the RSVF positions of the F₁ polypeptide, as well as the amino acid insertion,listed in one or more of rows 41, 42, or, 43 of column 2 of Table 5. Infurther embodiments, the PreF antigen includes a recombinant RSV Fprotein including a disulfide bond between cysteine residues that areintroduced by the F₁ polypeptide amino acid substitutions, as well asthe amino acid insertion, listed in of one or more of rows 41, 42, or,43 of column 3 of Table 5.

In one example, the PreF antigen includes a recombinant RSV F proteinstabilized in a prefusion conformation includes a disulfide bond betweencysteines at F1 positions 155 and 290, such as a recombinant F1polypeptide protein with S155C and S290C substitutions.

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including a combination of two or more of the disulfide bondsbetween cysteine residues listed in Table 5 or Table 5b, wherein thePreF antigen is specifically bound by a prefusion-specific antibody(e.g., D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø). It is understood that somecombinations will not result in a RSV F protein stabilized in aprefusion conformation; such combinations can be identified by methodsdisclosed herein, for example by confirming that the antigen containingsuch a polypeptide is specifically bound by a prefusion-specificantibody (e.g., D25 or AM22 antibody), and/or includes a RSV F prefusionspecific conformation (such as antigenic site Ø)

In further embodiments, the PreF antigen includes a recombinant RSV Fprotein including a non-natural disulfide bond stabilizing the F proteinin a prefusion conformation, wherein the F protein includes thesubstitutions listed in one of row 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,12, 13, 14, 15, or 16 of column 3 of Table 5b, wherein cysteine residuesare inserted in the F protein for formation of the non-natural disulfidebond. In any of these embodiments, the PreF antigen is specificallybound by a prefusion-specific antibody (e.g., D25 or AM22 antibody),and/or includes a RSV F prefusion specific conformation (such asantigenic site Ø).

The SEQ ID NOs listed in column 4 of Table 5b set forth amino acidsequences including the indicated substitutions, as well as, a signalpeptide, F₂ polypeptide (positions 26-109), a pep27 polypeptide(positions 110-136), a F₁ polypeptide (positions 137-513), atrimerization domain (a Foldon domain) and a thrombin cleavage site(LVPRGS (positions 547-552 of SEQ ID NO: 185)) and purification tags(his-tag (HHHHHH (positions 553-558 of SEQ ID NO: 185)) and Strep Tag II(SAWSHPQFEK (positions 559-568 of SEQ ID NO: 185))). Thus, in additionalembodiments, the PreF antigen includes a RSV F protein including a F₁polypeptide and a F₂ polypeptide as set forth in any one of the SEQ IDNOs listed in column 4 of Table 5b, such as a SEQ ID NO listed in one ofrow 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 of column 4of Table 5b, wherein the PreF antigen is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ). For example, the PreF antigen can include a RSV F protein includinga F₁ polypeptide and a F₂ polypeptide, wherein the F₂ and the F₁polypeptide include the amino acid sequence set forth as positions26-109 and 137-513, respectively, of any one of the SEQ ID NOs listed incolumn 4 of Table 5b, such as a SEQ ID NO listed in one of row 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16 of column 4 of Table 5b,wherein the PreF antigen is specifically bound by a prefusion-specificantibody (e.g., D25 or AM22 antibody), and/or includes a RSV F prefusionspecific conformation (such as antigenic site Ø).

TABLE 5b Exemplary stabilized F protein substitutions and sequencesDescription Substitutions SEQ ID NO: 1 Intrachain disulfide S238C, E92C421 2 Intrachain disulfide L193C, I59C 422 3 Intrachain disulfide I59C,L297C 423 4 Intrachain disulfide L297C, I292C 424 5 Intrachain disulfideK176C, S190C 425 6 Intrachain disulfide T189C, A177C 426 7 Intrachaindisulfide T58C, K191C 427 8 Intrachain disulfide A424C, V450C 428 9Intrachain disulfide L171C, K191C 429 10 Intrachain disulfide K176C,S190C 430 11 Interchain disulfide K77C, I217C 431 12 Intrachaindisulfide K427C, D448C 434 13 Intrachain disulfide G151C, N302C 435 14Intrachain disulfide G151C, V300C 436 15 Intrachain disulfide T189C,V56C 437 16 Intrachain disulfide L171C, K191C 438

ii. Cavity Filling Amino Acid Substitutions

Comparison of the structure of the prefusion conformation of the RSV Fprotein (e.g., in complex with D25 Fab as disclosed herein) to thestructure of the postfusion RSV F protein (disclosed, e.g., in asdisclosed in McLellan et al., J. Virol., 85, 7788, 2011) identifiesseveral internal cavities or pockets in the prefusion conformation thatmust collapse for F to transition to the postfusion conformation. Thesecavities include those listed in Table 6.

Accordingly, in several embodiments, the PreF antigen includes arecombinant RSV F protein stabilized in a prefusion conformation by oneor more amino acid substitutions that introduce an amino acid thatreduces the volume of an internal cavity that collapses in thepostfusion conformation of RSV F protein. For example, cavities arefilled by substituting amino acids with large side chains for those withsmall side chains. The cavities can be intra-protomer cavities, orinter-protomer cavities. One example of a RSV F cavity filling aminoacid substitution to stabilize the RSV protein in its prefusionconformation a RSV F protein with 190F and V207L substitutions. Inanother embodiment, the cavity filling amino acid substitution tostabilize the RSV protein in its prefusion conformation a RSV F proteinincludes a S190F, S190L, S190W, S190H, S190M, or 190Y substitution.

The person of ordinary skill in the art can use methods provided hereinto compare the structures of the pre- and post-fusion conformations ofthe RSV F protein to identify suitable cavities, and amino acidsubstitutions for filling the identified cavities. Exemplary cavitiesand amino acid substitutions for reducing the volume of these cavitiesare provided in Table 6.

TABLE 6 Exemplarity cavity-filling amino acid substitutions RowCavity/Cavities A.A. Substitutions SEQ ID NO: 1 Ser190 and Val207 190Fand 207L 191 2 Val207 207L and 220L 193 3 Ser190 and Val296 296F and190F 196 4 Ala153 and Val207 220L and 153W 197 5 Val207 203W 248 6Ser190 and Val207 83W and 260W 192 7 Val296 58W and 298L 195 8 Val90 87Fand 90L 194 9 Ser190 190F, 190L, 190W, 190H, 190M, or 190Y

The indicated cavities are referred to by a small residue abutting thecavity that can be mutated to a larger residue to fill the cavity. Itwill be understood that other residues (besides the one the cavity isnamed after) could also be mutated to fill the same cavity.

Thus, in some embodiments, the PreF antigen includes a recombinant RSV Fprotein including one or more amino acid substitutions that reduce thevolume of one or more of the cavities listed in column 2 of Table 6,wherein the PreF antigen is specifically bound by a prefusion-specificantibody (e.g., D25 or AM22 antibody), and/or includes a RSV F prefusionspecific conformation (such as antigenic site Ø). In additionalembodiments, the PreF antigen includes a recombinant RSV F proteinincluding one or more of the amino acid substitutions listed in of row1, 2, 3, 4, 5, 6, 7, 8, or 9 of column 3 of Table 6, wherein the PreFantigen is specifically bound by a prefusion-specific antibody (e.g.,D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø).

The SEQ ID NOs listed in Table 6 set forth amino acid sequencesincluding the indicated substitutions, as well as, a signal peptide, F₂polypeptide (positions 26-109), a pep27 polypeptide (positions 110-136),a F₁ polypeptide (positions 137-513), a trimerization domain (a Foldondomain) and a thrombin cleavage site (LVPRGS (positions 547-552 of SEQID NO: 185)) and purification tags (his-tag (HHHHHH (positions 553-558of SEQ ID NO: 185)) and Strep Tag II (SAWSHPQFEK (positions 559-568 ofSEQ ID NO: 185))). Thus, in additional embodiments, the PreF antigenincludes a recombinant RSV F protein including a F₁ polypeptide and a F₂polypeptide as set forth in any one of the SEQ ID NOs listed in of row1, 2, 3, 4, 5, 6, 7 or 8 of column 4 of Table 6, wherein the PreFantigen is specifically bound by a prefusion-specific antibody (e.g.,D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø). For example, the PreF antigencan include a recombinant RSV F protein including a F₁ polypeptide and aF₂ polypeptide as set forth as positions 26-109 and 137-513,respectively, as set forth in any one of the SEQ ID NOs listed in of row1, 2, 3, 4, 5, 6, 7, or 8 of column 4 of Table 6, wherein the PreFantigen is specifically bound by a prefusion-specific antibody (e.g.,D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø).

In additional embodiments, the PreF antigen includes a recombinant RSV Fprotein including the amino acid substitutions listed in one of row 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39,40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57,58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75,76, 77, 78, 79, 80, 81, 82, 83 or 84 of column 3 of Table 6b, whereinthe PreF antigen is specifically bound by a prefusion-specific antibody(e.g., D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø).

The SEQ ID NOs listed in Table 6a set forth amino acid sequencesincluding the indicated substitutions a signal peptide, F2 polypeptide(positions 26-109), a pep27 polypeptide (positions 110-136), a F₁polypeptide (positions 137-513), a trimerization domain (a Foldondomain) and a thrombin cleavage site (LVPRGS (positions 547-552 of SEQID NO: 185)) and purification tags (his-tag (HHHHHH (positions 553-558of SEQ ID NO: 185)) and Strep Tag II (SAWSHPQFEK (positions 559-568 ofSEQ ID NO: 185))). Thus, in additional embodiments, the PreF antigenincludes a recombinant RSV F protein including a F₁ polypeptide and a F₂polypeptide as set forth in any one of the SEQ ID NOs listed in one ofrow 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37,38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55,56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73,74, 75, 76, 77, 78, 79, 80, 81, 82, 83, or 84 of column 4 of Table 6b,wherein the PreF antigen is specifically bound by a prefusion-specificantibody (e.g., D25 or AM22 antibody), and/or includes a RSV F prefusionspecific conformation (such as antigenic site Ø). For example, the PreFantigen can include a recombinant RSV F protein including a F₁polypeptide and a F₂ polypeptide as set forth as positions 26-109 and137-513, respectively, as set forth in any one of the SEQ ID NOs listedin one of row 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53,54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71,72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, or 84 of column 4 ofTable 6b, wherein the PreF antigen is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ).

TABLE 6b Exemplarity cavity-filling amino acid substitution SEQ IDDescription Mutations NO 1 Cavity filling L230F 391 2 Cavity fillingL158F 392 3 Cavity filling L230F, L158F 393 4 Cavity filling L203F 395 5Cavity filling V187F 396 6 Cavity filling Y198F 397 7 Cavity fillingY198W 398 8 Cavity filling L204F 399 9 Cavity filling Y53F, L188F 400 10Cavity filling V187F, L203F 401 11 Cavity filling Y198F, L203F 402 12Cavity filling L141W 403 13 Cavity filling L142F 404 14 Cavity fillingL142W 405 15 Cavity filling V144F 406 16 Cavity filling V144W 407 17Cavity filling V90F 408 18 Cavity filling L83F 409 19 Cavity fillingV185F, T54A 410 20 Cavity filling I395F 411 21 Cavity filling V90F,V185F, T54A 412 22 Cavity filling L83F, V90F 413 23 Cavity filling L83F,V185F, T54A 414 24 Cavity filling L230F, V90F, I395F 415 25 Cavityfilling I395F, V185F, T54A 416 26 Cavity filling L203F, V90F, L230F,L158F, 417 S509F, I395F, V185F, T54A 27 Cavity filling I221Y 419 28cavity filling F140W 439 29 cavity filling F137W 440 30 cavity fillingS190L, V192L 441 31 cavity filling V187F, S190L, V192L 442 32 cavityfilling V187L, S190L, V192L 443 33 cavity filling V185F V187L S190LV192L 444 34 cavity filling V154L, V157L, V185L, V187L 445 35 cavityfilling V154L, V185L, V187L 446 36 cavity filling V187F 447 37 cavityfilling T58L A298L 448 38 cavity filling T58L V154L V185L V187L A298L449 39 cavity filling Y458W 450 40 cavity filling L158F, I167A 451 41cavity filling L158W, I167A 452 42 cavity filling L158F 453 cavityfilling L158W 454 43 cavity filling V56L, I167L, A298L 455 44 cavityfilling V56L, I167L, A298M 456 45 cavity filling V56L, A167L 457 46cavity filling I167F 458 47 cavity filling I167M 459 48 cavity fillingV154F 460 49 cavity filling V56L, I167L, A298L, V154F 461 50 cavityfilling I199L, L203F 462 51 cavity filling I199L, L203F, P205Q, I206T463 52 cavity filling I199L, L203F, P205E, I206K 464 53 cavity fillingI199L, L203F, V207F 465 54 cavity filling I199L, L203F, P205Q, I206T,V207F 466 55 cavity filling I199L, L203F, P205E, I206K, V207F 467 56cavity filling I199L, L203F, L83F 468 57 cavity filling I199L, L203F,P205Q, I206T, L83F 469 58 cavity filling I199L, L203F, P205E, I206K,L83F 470 59 cavity filling I199L, L203F, S190L, V192L 471 60 cavityfilling I199L, L203F, P205Q, I206T, V187F, 472 S190L, V192L 61 cavityfilling S55A, S190M, L203F, V207I, V296I 473 62 cavity filling Y53F,S55A, K176I, S190L, V207I, 474 S259L, D263L, V296I 63 cavity fillingL158F, V207M, V296I 475 64 cavity filling V56L, V207M, V296I 476 65cavity filling V56L, V207I, V296I 477 66 cavity filling V56I, V207M,V296I 478 67 cavity filling V154L, V207M, V296I 479 68 cavity fillingY198F, V207I, T219W, V296I 480 69 cavity filling Y198F, V207I, T219I,V296I 481 70 cavity filling Y198F, V207M, T219W, V296I 482 71 cavityfilling Y198F, V207M, T219I, V296I 483 72 cavity filling Y198F, V207M,T219L, V296I 484 73 Cavity filling S190Y 432 74 Cavity filling S190W 43375 cavity filling I206F, V207M, T219V, V296I 487 76 cavity fillingY198F, V207M, T219L, K226M 488 77 cavity filling Y198F, V207M, T219L,K226W 489 78 cavity filling Y198F, V207M, T219L, K226L 490 79 cavityfilling L158F, L203F, V207I, V296I 497 80 cavity filling F488W 498 81Cavity filling F488R 499 82 Cavity filling V207L 500 test 207L 83 Cavityfilling S190F 501 test 207L 84 Cavity filling S190M 502

iii. Repacking Substitutions

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a prefusion conformation by one or more repackingamino acid substitutions. Repacking substitutions increase attractiveinteractions (such as hydrophobic interactions or hydrogen-bondformation), or decrease repulsive interactions (such as repulsive forcesbetween clusters of similarly charged residues), between amino acids ina protein.

The person of ordinary skill in the art can use methods provided hereinto compare the structures of the pre- and post-fusion conformations ofthe RSV F protein to identify suitable sites of repulsive and/orattractive interactions between RSV F protein residues, and amino acidsubstitutions for reducing or increasing these interactions,respectively. For example, by identifying repulsive interactions in thestructure of the RSV F protein in the prefusion conformation providedherein, and introducing substitutions that reduce these repulsiveinteractions. Alternatively, the RSV F protein can include substitutionsthat increase attractive interactions between RSV F protein residues inthe prefusion conformation of the RSV F protein, but not the postfusionconformation of the RSV F protein. Exemplary amino acid substitutionsare provided in Table 7.

TABLE 7 Repacking Amino Acid Substitutions Row Substitutions SEQ ID NO 1I64L, I79V, Y86W, L193V, L195F, Y198F, I199F, L203F, V207L, I214L 227 2I64L, I79L, Y86W, L193V, L195F, Y198F, I199F, L203F, I214L 228 3 I64W,I79V, Y86W, L193V, L195F, Y198F, I199F, L203F, V207L, I214L 229 4 I79V,Y86F, L193V, L195F, Y198F, I199F, L203F, V207L, I214L 230 5 I64V, I79V,Y86W, L193V, L195F, Y198F, I199Y, L203F, V207L, I214L 231 6 I64F, I79V,Y86W, L193V, L195F, Y198F, I199F, L203F, V207L, I214L 232 7 I64L, I79V,Y86W, L193V, L195F, I199F, L203F, V207L, I214L 233 8 V56I, T58I, V164I,L171I, V179L, L181F, V187I, I291V, V296I, A298I 234 9 V56I, T58I, V164I,V179L, T189F, I291V, V296I, A298I 235 10 V56L, T58I, L158W, V164L,I167V, L171I, V179L, L181F, V187I, I291V, V296L 236 11 V56L, T58I,L158Y, V164L, I167V, V187I, T189F, I291V, V296L 237 12 V56I, T58W,V164I, I167F, L171I, V179L, L181V, V187I, I291V, V296I 238 13 V56I,T58I, I64L, I79V, Y86W, V164I, V179L, T189F, L193V, L195F, Y198F, I199F,239 L203F, V207L, I214L, I291V, V296I, A298I 14 V56I, T58I, I79V, Y86F,V164I, V179L, T189F, L193V, L195F, Y198F, I199F, L203F, 240 V207L,I214L, I291V, V296I, A298I 15 V56I, T58W, I64L, I79V, Y86W, V164I,I167F, L171I, V179L, L181V, V187I, L193V, 241 L195F, Y198F, I199F,L203F, V207L, I214L, I291V, V296I 16 V56I, T58W, I79V, Y86F, V164I,I167F, L171I, V179L, L181V, V187I, L193V, L195F, 242 Y198F, I199F,L203F, V207L, I214L, I291V, V296I 17 D486N, E487Q, D489N, and S491A 24918 D486H, E487Q, and D489H 250 19 T400V, D486L, E487L, and D489L 251 20T400V, D486I, E487L, and D489I, 252 21 T400V, S485I, D486L, E487L,D489L, Q494L, and K498L 253 23 T400V, S485I, D486I, E487L, D489I, Q494L,and K498L 254 24 K399I, T400V, S485I, D486L, E487L, D489L, Q494L, E497L,and K498L 255 25 K399I, T400V, S485I, D486I, E487L, D489I, Q494L, E497L,and K498L 256 26 L375W, Y391F, and K394M 286 27 L375W, Y391F, and K394W287 28 L375W, Y391F, K394M, D486N, E487Q, D489N, and S491A 288 29 L375W,Y391F, K394M, D486H, E487Q, and D489H 289 30 L375W, Y391F, K394W, D486N,E487Q, D489N, and S491A 290 31 L375W, Y391F, K394W, D486H, E487Q, andD489H 291 32 L375W, Y391F, K394M, T400V, D486L, E487L, D489L, Q494L, andK498M 292 33 L375W, Y391F, K394M, T400V, D486I, E487L, D489I, Q494L, andK498M 293 34 L375W, Y391F, K394W, T400V, D486L, E487L, D489L, Q494L, andK498M 294 35 L375W, Y391F, K394W, T400V, D486I, E487L, D489I, Q494L, andK498M 295 36 F137W and R339M 326 37 F137W and F140W 327 38 F137W, F140W,and F488W 328 39 D486N, E487Q, D489N, S491A, and F488W 329 40 D486H,E487Q, D489H, and F488W 330 41 T400V, D486L, E487L, D489L, and F488W 33142 T400V, D486I, E487L, D489I, and F488W 332 43 D486N, E487Q, D489N,S491A, F137W, and F140W 333 44 D486H, E487Q, D489H, F137W, and F140W 33445 T400V, D486L, E487L, D489L, F137W, and F140W 335 46 L375W, Y391F,K394M, F137W, and F140W 336 47 L375W, Y391F, K394M, F137W, F140W, andR339M 337

Thus, in some embodiments, the PreF antigen includes a recombinant RSV Fprotein including the amino acid substitutions listed in one of row 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39,40, 41, 42, 43, 44, 45, 46, or 47 of column 2 of Table 7, wherein thePreF antigen is specifically bound by a prefusion-specific antibody(e.g., D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø).

The SEQ ID NOs listed in Table 7 set forth amino acid sequencesincluding the indicated substitutions, as well as, a signal peptide, F₂polypeptide (positions 26-109), a pep27 polypeptide (positions 110-136),a F₁ polypeptide (positions 137-513), a trimerization domain (a Foldondomain) and a thrombin cleavage site (LVPRGS (positions 547-552 of SEQID NO: 185)) and purification tags (his-tag (HHHHHH (positions 553-558of SEQ ID NO: 185)) and Strep Tag II (SAWSHPQFEK (positions 559-568 ofSEQ ID NO: 185))). Thus, in additional embodiments, the PreF antigenincludes a recombinant RSV F protein including a F₁ polypeptide and a F₂polypeptide as set forth in one of rows 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46,or 47 of column 3 of Table 7, wherein the PreF antigen is specificallybound by a prefusion-specific antibody (e.g., D25 or AM22 antibody),and/or includes a RSV F prefusion specific conformation (such asantigenic site Ø). For example, the PreF antigen can include arecombinant RSV F protein including a F₁ polypeptide and a F₂polypeptide as set forth as positions 26-109 and 137-513, respectively,as set forth in any one of the SEQ ID NOs listed in one of rows 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,41, 42, 43, 44, 45, 46, or 47 of column 3 of Table 7, wherein the PreFantigen is specifically bound by a prefusion-specific antibody (e.g.,D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø).

Several embodiments include combinations of the amino acid substitutionslisted above.

iv. N-Linked Glycosylation Sites

Comparison of the structure of the prefusion conformation of the RSV Fprotein (e.g., in complex with D25 or AM22 as disclosed herein) to thestructure of the postfusion RSV F protein (disclosed, e.g., in asdisclosed in McLellan et al., J. Virol., 85, 7788, 2011) identifiesseveral regions of the RSV F protein that are solvent-accessible in theprefusion RSV F conformation described herein, but solvent-inaccessiblein the postfusion RSV F conformation (as disclosed in McLellan et al.,J. Virol., 85, 7788, 2011).

Thus, in some embodiments, the PreF antigen includes a recombinant RSV Fprotein including an amino acid substitution that introduces an N-linkedglycosylation site at a position that is solvent-accessible in theprefusion RSV F conformation described herein, but solvent-inaccessiblein the postfusion RSV F conformation (as disclosed in McLellan et al.,J. Virol., 85, 7788, 2011). These amino acid substitutions stabilize therecombinant RSV F protein in the prefusion conformation by increasingthe energy required for the protein to adopt the postfusion state.

To create an N-linked glycosylation site, the sequence Asn-X-Ser/Thr(where X is any amino acid except Pro) needs to be introduced. This canbe accomplished by substitution of a Ser/Thr amino acid two residuesC-terminal to a native Asn residue, or by substitution of an Asn aminoacid two residues N-terminal to a native Ser/Thr residue, or bysubstitution of both an Asn and Ser/Thr residue separated by onenon-proline amino acid. Thus, in several embodiments, any of thedisclosed recombinant RSV F proteins are glycosylated. For example, theRSV F protein includes an amino acid substitution that introduces aN-linked glycosylation site in the RSV F protein that issolvent-accessible in the prefusion RSV F conformation disclosed hereinbut solvent-inaccessible in the postfusion conformation of RSV F asdisclosed in McLellan et al., J. Virol., 85, 7788, 2011). ExemplaryN-linked glycosylation site modifications are provided in Table 8.

TABLE 8 Exemplary N-linked glycosylation N-linked glycosylation siteExemplary SEQ Row position Exemplary substitutions ID NO 1 506 I506N andK508T 198 2 175 A177S 199 3 178 V178N 200 4 276 V278T 203 5 476 Y478T204 6 185 V185N and V187T 214 7 160 L160N and G162S 215 8 503 L503N anda F505S 216 9 157 V157N 217

In some embodiments, a PreF antigen includes a recombinant RSV F proteinstabilized in a prefusion conformation by a N-linked glycosylation siteat one or more of (such as 2, 3, 4, 5, 6, 7, 8, or 9 of) positions 506,175, 178, 276, 476, 185, 160, 503, or 157 of the F₁ polypeptide, whereinthe PreF antigen is specifically bound by a prefusion-specific antibody(e.g., D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø). For example, the F₁ polypeptidecan include an amino acid substitution that introduces an N-linkedglycosylation site at one or more of (such as 2, 3, 4, 5, 6, 7, 8, or 9of) positions 506, 175, 178, 276, 476, 185, 160, 503, or 157 of the F₁polypeptide.

The SEQ ID NOs listed in Table 8 set forth amino acid sequencesincluding the indicated substitutions, as well as, a signal peptide, F₂polypeptide (positions 26-109), a pep27 polypeptide (positions 110-136),a F₁ polypeptide (positions 137-513), a trimerization domain (a Foldondomain) and a thrombin cleavage site (LVPRGS (positions 547-552 of SEQID NO: 185)) and purification tags (his-tag (HHHHHH (positions 553-558of SEQ ID NO: 185)) and Strep Tag II (SAWSHPQFEK (positions 559-568 ofSEQ ID NO: 185))). In some embodiments, the PreF antigen includes a F₁polypeptide including I506N and K508T substitutions to introduce aN-linked glycosylation site at position 506. In some embodiments, thePreF antigen includes a F₁ polypeptide including an A177S substitutionto introduce a N-linked glycosylation site at position 175. In someembodiments, the PreF antigen includes a F₁ polypeptide including aV178N substitution to introduce a N-linked glycosylation site atposition 178. In some embodiments, the PreF antigen includes a F₁polypeptide including a V278T substitution to introduce a N-linkedglycosylation site at position 276. In some embodiments, the PreFantigen includes a F₁ polypeptide including a Y478T substitution tointroduce a N-linked glycosylation site at position 476. In someembodiments, the PreF antigen includes a F₁ polypeptide including V185Nand V187T substitutions to introduce a N-linked glycosylation site atposition 185. In some embodiments, the PreF antigen includes a F₁polypeptide including L160N and G162S substitutions to introduce aN-linked glycosylation site at position 160. In some embodiments, thePreF antigen includes a F₁ polypeptide including L503N and F505Ssubstitutions to introduce a N-linked glycosylation site at position503. In some embodiments, the PreF antigen includes a F₁ polypeptideincluding a V157N substitution to introduce a N-linked glycosylationsite at position 157. In any of these embodiments, the PreF antigen isspecifically bound by a prefusion-specific antibody (e.g., D25 or AM22antibody), and/or includes a RSV F prefusion specific conformation (suchas antigenic site Ø)

In additional embodiments, the F₁ polypeptide comprises residues 137-513of SEQ ID NO: 198 (N-linked glycosylation site at position 506); SEQ IDNO: 199 (N-linked glycosylation site at position 175); SEQ ID NO: 200(N-linked glycosylation site at position 178); SEQ ID NO: 203 (N-linkedglycosylation site at position 276); SEQ ID NO: 204 (N-linkedglycosylation site at position 476); SEQ ID NO: 214 (N-linkedglycosylation site at position 185); SEQ ID NO: 215 (N-linkedglycosylation site at position 160); SEQ ID NO: 216 (N-linkedglycosylation site at position 503); or SEQ ID NO: 217 (N-linkedglycosylation site at position 157), wherein the PreF antigen isspecifically bound by a prefusion-specific antibody (e.g., D25 or AM22antibody), and/or includes a RSV F prefusion specific conformation (suchas antigenic site Ø).

Methods of making glycosylated polypeptides are disclosed herein and arefamiliar to the person of ordinary skill in the art. For example, suchmethods are described in U.S. Patent Application Pub. No. 2007/0224211,U.S. Pat. Nos. 7,029,872; 7,834,159, 7,807,405, Wang and Lomino, ACSChem. Biol., 7:110-122, 2011, and Nettleship et al., Methods Mol. Biol,498:245-263, 2009, each of which is incorporated by reference herein. Insome embodiments, glycosylated PreF antigens are produced by expressingthe recombinant RSV F protein in mammalian cells, such as HEK293 cellsor derivatives thereof, such as GnTI^(−/−) cells (ATCC® No. CRL-3022).In some embodiments, the RSV F protein antigens are produced byexpression the RSV F protein antigens in mammalian cells, such as HEK293cells or derivatives thereof, with swainsonine added to the media inorder to inhibit certain aspects of the glycosylation machinery, forexample to promote production of hybrid glycans.

In several embodiments, the F1 polypeptide includes two or more of theN-linked glycosylation sites listed in Table 8.

v. Exemplary Stabilizing Modifications

The person of skill in the art will appreciate that the PreF antigen caninclude a recombinant RSV F protein stabilized in a prefusionconformation by combinations of one or more of the stabilizing aminoacid substitutions described herein, such as a combination of amino acidsubstitutions that introduce one or more disulfide bonds, fill cavitieswithin the RSV F protein, alter the packing of residues in the RSV Fprotein, introduce N-linked glycosylation sites. For example, in severalembodiments, recombinant RSV F protein includes amino acid substitutionsthat introduce a disulfide bond, and that fill cavities within the RSV Fprotein.

In some embodiments, a recombinant RSV F protein stabilized in aprefusion conformation includes a disulfide bond between a pair ofcysteines at positions 155 and 290, and a cavity-filling amino acidsubstitution at position 190; or a disulfide bond between a pair ofcysteines at positions 155 and 290, a cavity-filling amino acidsubstitution at position 190, and a cavity-filling amino acidsubstitution at position 207. For example, the cavity fillingsubstitution at position 190 and/or position 207 can be a large aromaticor hydrophobic amino acid substitution (such as tyrosine, leucine,phenylalanine, histidine, or tryptophan).

In some embodiments, the F1 polypeptide of the recombinant RSV F proteinincludes S155C, S290C, and S190F amino acid substitutions. In someembodiments, the F1 polypeptide of the recombinant RSV F proteinincludes S155C, S290C, and S190W amino acid substitutions. In someembodiments, the F1 polypeptide of the recombinant RSV F proteinincludes S155C, S290C, and S190L amino acid substitutions. In someembodiments, the F1 polypeptide of the recombinant RSV F proteinincludes S155C, S290C, S190F, and V207L amino acid substitutions. Insome embodiments, the F1 polypeptide of the recombinant RSV F proteinincludes S155C, S290C, S190W, and V207L amino acid substitutions. Insome embodiments, the F1 polypeptide of the recombinant RSV F proteinincludes S155C, S290C, S190L, and V207L amino acid substitutions.

In some embodiments, the F1 polypeptide of the recombinant RSV F proteinincludes S155C, S290C, S190F, and V207F amino acid substitutions. Insome embodiments, the F1 polypeptide of the recombinant RSV F proteinincludes S155C, S290C, S190W, and V207F amino acid substitutions. Insome embodiments, the F1 polypeptide of the recombinant RSV F proteinincludes S155C, S290C, S190L, and V207F amino acid substitutions. Insome embodiments, the F1 polypeptide of the recombinant RSV F proteinincludes S155C, S290C, S190F, and V207W amino acid substitutions. Insome embodiments, the F1 polypeptide of the recombinant RSV F proteinincludes S155C, S290C, S190W, and V207W amino acid substitutions. Insome embodiments, the F1 polypeptide of the recombinant RSV F proteinincludes S155C, S290C, S190L, and V207W amino acid substitutions.

In several embodiments, the recombinant RSV F protein stabilized in aprefusion conformation includes a F₁ polypeptide and a F₂ polypeptidefrom a human RSV A subtype, a human RSV B subtype, or a bovine RSV,wherein the F₁ polypeptide includes including one of the abovecombinations of stabilizing substitutions.

In some embodiments, the recombinant RSV F protein stabilized in aprefusion conformation includes a F₂ polypeptide and a F₁ polypeptideincluding positions 26-109 and 137-513, respectively, of any one of SEQID NOs: 1-184 or 370, and further includes S155C, S290C, and S190F aminoacid substitutions. In some embodiments, the recombinant RSV F proteinstabilized in a prefusion conformation includes a F₂ polypeptide and aF₁ polypeptide including positions 26-109 and 137-513, respectively, ofany one of SEQ ID NOs: 1-184 or 370, and further includes S155C, S290C,and S190W amino acid substitutions. In some embodiments, the recombinantRSV F protein stabilized in a prefusion conformation includes a F₂polypeptide and a F₁ polypeptide including positions 26-109 and 137-513,respectively, of any one of SEQ ID NOs: 1-184 or 370, and furtherincludes S155C, S290C, and S190L amino acid substitutions. In someembodiments, the recombinant RSV F protein stabilized in a prefusionconformation includes a F₂ polypeptide and a F₁ polypeptide includingpositions 26-109 and 137-513, respectively, of any one of SEQ ID NOs:1-184 or 370, and further includes S155C, S290C, and S190H amino acidsubstitutions. In some embodiments, the recombinant RSV F proteinstabilized in a prefusion conformation includes a F₂ polypeptide and aF₁ polypeptide including positions 26-109 and 137-513, respectively, ofany one of SEQ ID NOs: 1-184 or 370, and further includes S155C, S290C,and S190M amino acid substitutions. In some embodiments, the recombinantRSV F protein stabilized in a prefusion conformation includes a F₂polypeptide and a F₁ polypeptide including positions 26-109 and 137-513,respectively, of any one of SEQ ID NOs: 1-184 or 370, and furtherincludes S155C, S290C, and S190Y amino acid substitutions.

In some embodiments, the recombinant RSV F protein stabilized in aprefusion conformation includes a F₂ polypeptide and a F₁ polypeptideincluding positions 26-109 and 137-513, respectively, of any one of SEQID NOs: 1-184 or 370, and further includes S155C, S290C, S190F, andV207L amino acid substitutions. In some embodiments, the recombinant RSVF protein stabilized in a prefusion conformation includes a F₂polypeptide and a F₁ polypeptide including positions 26-109 and 137-513,respectively, of any one of SEQ ID NOs: 1-184 or 370, and furtherincludes S155C, S290C, S190W, and V207L amino acid substitutions. Insome embodiments, the recombinant RSV F protein stabilized in aprefusion conformation includes a F₂ polypeptide and a F₁ polypeptideincluding positions 26-109 and 137-513, respectively, of any one of SEQID NOs: 1-184 or 370, and further includes S155C, S290C, S190L, andV207L amino acid substitutions. In some embodiments, the recombinant RSVF protein stabilized in a prefusion conformation includes a F₂polypeptide and a F₁ polypeptide including positions 26-109 and 137-513,respectively, of any one of SEQ ID NOs: 1-184 or 370, and furtherincludes S155C, S290C, S190H, and V207L amino acid substitutions. Insome embodiments, the recombinant RSV F protein stabilized in aprefusion conformation includes a F₂ polypeptide and a F₁ polypeptideincluding positions 26-109 and 137-513, respectively, of any one of SEQID NOs: 1-184 or 370, and further includes S155C, S290C, S190M, andV207L amino acid substitutions. In some embodiments, the recombinant RSVF protein stabilized in a prefusion conformation includes a F₂polypeptide and a F₁ polypeptide including positions 26-109 and 137-513,respectively, of any one of SEQ ID NOs: 1-184 or 370, and furtherincludes S155C, S290C, S190Y, and V207L amino acid substitutions.

In some embodiments, the recombinant RSV F protein stabilized in aprefusion conformation includes a F₂ polypeptide and a F₁ polypeptideincluding positions 26-109 and 137-513, respectively, of any one of SEQID NOs: 1-184 or 370, and further includes S155C, S290C, S190F, andV207F amino acid substitutions. In some embodiments, the recombinant RSVF protein stabilized in a prefusion conformation includes a F₂polypeptide and a F₁ polypeptide including positions 26-109 and 137-513,respectively, of any one of SEQ ID NOs: 1-184 or 370, and furtherincludes S155C, S290C, S190W, and V207F amino acid substitutions. Insome embodiments, the recombinant RSV F protein stabilized in aprefusion conformation includes a F₂ polypeptide and a F₁ polypeptideincluding positions 26-109 and 137-513, respectively, of any one of SEQID NOs: 1-184 or 370, and further includes S155C, S290C, S190L, andV207F amino acid substitutions. In some embodiments, the recombinant RSVF protein stabilized in a prefusion conformation includes a F₂polypeptide and a F₁ polypeptide including positions 26-109 and 137-513,respectively, of any one of SEQ ID NOs: 1-184 or 370, and furtherincludes S155C, S290C, S190H, and V207F amino acid substitutions. Insome embodiments, the recombinant RSV F protein stabilized in aprefusion conformation includes a F₂ polypeptide and a F₁ polypeptideincluding positions 26-109 and 137-513, respectively, of any one of SEQID NOs: 1-184 or 370, and further includes S155C, S290C, S190M, andV207F amino acid substitutions. In some embodiments, the recombinant RSVF protein stabilized in a prefusion conformation includes a F₂polypeptide and a F₁ polypeptide including positions 26-109 and 137-513,respectively, of any one of SEQ ID NOs: 1-184 or 370, and furtherincludes S155C, S290C, S190Y, and V207F amino acid substitutions.

In some embodiments, the recombinant RSV F protein stabilized in aprefusion conformation includes a F₂ polypeptide and a F₁ polypeptideincluding positions 26-109 and 137-513, respectively, of any one of SEQID NOs: 1-184 or 370, and further includes S155C, S290C, S190F, andV207W amino acid substitutions. In some embodiments, the recombinant RSVF protein stabilized in a prefusion conformation includes a F₂polypeptide and a F₁ polypeptide including positions 26-109 and 137-513,respectively, of any one of SEQ ID NOs: 1-184 or 370, and furtherincludes S155C, S290C, S190W, and V207W amino acid substitutions. Insome embodiments, the recombinant RSV F protein stabilized in aprefusion conformation includes a F₂ polypeptide and a F₁ polypeptideincluding positions 26-109 and 137-513, respectively, of any one of SEQID NOs: 1-184 or 370, and further includes S155C, S290C, S190L, andV207W amino acid substitutions. In some embodiments, the recombinant RSVF protein stabilized in a prefusion conformation includes a F₂polypeptide and a F₁ polypeptide including positions 26-109 and 137-513,respectively, of any one of SEQ ID NOs: 1-184 or 370, and furtherincludes S155C, S290C, S190H, and V207W amino acid substitutions. Insome embodiments, the recombinant RSV F protein stabilized in aprefusion conformation includes a F₂ polypeptide and a F₁ polypeptideincluding positions 26-109 and 137-513, respectively, of any one of SEQID NOs: 1-184 or 370, and further includes S155C, S290C, S190M, andV207W amino acid substitutions. In some embodiments, the recombinant RSVF protein stabilized in a prefusion conformation includes a F₂polypeptide and a F₁ polypeptide including positions 26-109 and 137-513,respectively, of any one of SEQ ID NOs: 1-184 or 370, and furtherincludes S155C, S290C, S190Y, and V207W amino acid substitutions.

In some embodiments, the recombinant RSV F protein stabilized in aprefusion conformation includes a F₂ polypeptide and a F₁ polypeptideincluding positions 26-109 and 137-513, respectively, of any one of SEQID NOs: 1-184 or 370, and further includes S155C, S290C, S190F, V207L,and F488W amino acid substitutions. In some embodiments, the recombinantRSV F protein stabilized in a prefusion conformation includes a F₂polypeptide and a F₁ polypeptide including positions 26-109 and 137-513,respectively, of any one of SEQ ID NOs: 1-184 or 370, and furtherincludes S155C, S290C, S190F, and F488W amino acid substitutions.

In some embodiments, the recombinant RSV F protein stabilized in aprefusion conformation includes a F₂ polypeptide and a F₁ polypeptideincluding positions 26-109 and 137-513, respectively, of SEQ ID NO: 371(RSV A with S155C, S290C, S190F and V207L substitutions), SEQ ID NO: 372(RSV B with S155C, S290C, S190F and V207L substitutions), SEQ ID NO: 373(bovine RSV with S155C, S290C, S190F and V207L substitutions), SEQ IDNO: 374 (RSV A with S155C, S290C, and S190F substitutions), SEQ ID NO:375 (RSV B with S155C, S290C, and S190F substitutions); or SEQ ID NO:376 (bovine RSV with S155C, S290C, and S190F substitutions).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a prefusion conformation that includes the aminoacid substitutions listed in one of rows 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46,47, 48, 49, 50, 51, 52, 53, or 54 of column 3 of Table 8b. Thestabilized RSV F protein can be specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ).

TABLE 8b Exemplary recombinant RSV F protein substitutions and sequenceswith and without a C-terminal thrombin-cleavable Foldon domain WithWithout Thrombin- Foldon Cleavable domain Foldon SEQ ID domain SEQDescription Mutations NO ID NO 1 DSCav1 + Cavity filling + replace(S155C, S290, S190F, V207L) + 503 552 exposed hydrophobic residuesL503E/I506K 2 DSCav1 + Cavity filling + replace (S155C, S290, S190F,V207L) + 504 553 exposed hydrophobic residues L503E/I506K/F505W 3DSCav1 + Cavity filling + replace (S155C, S290, S190F, V207L) + 505 554exposed hydrophobic residues L503E/I506K/L230F/L158F 4 DSCav1 + Cavityfilling + replace (S155C, S290, S190F, V207L) + 506 555 exposedhydrophobic residues L503E/I506K/S509F/F505W/L230F/L158F 5 DSCav1 +replace exposed hydrophobic (S155C, S290, S190F, V207L) + 507 556residues L160K/V178T/L258K/V384T/I431S/L467Q/ 6 DSCav1 + replace exposedhydrophobic (S155C, S290, S190F, V207L) + 508 557 residuesF477K/L481Q/V482K/L503Q/I506K 7 DSCav1 + replace exposed hydrophobic(S155C, S290, S190F, V207L) + 509 558 residuesL160K/V178T/L258K/V384T/I431S/L467Q/ F477K/L481Q/V482K/L503Q/I506K 8DSCav1 + ds (S155C, S290, S190F, V207L) + 510 559 (L512C/L513C) 9DSCav1 + ds + replace exposed (S155C, S290, S190F, V207L) + 511 560hydrophobic residues (L512C/L513C) +L160K/V178T/L258K/V384T/I431S/L467Q/ 10 DSCav1 + ds + replace exposed(S155C, S290, S190F, V207L) + 512 561 hydrophobic residues(L512C/L513C) + F477K/L481Q/V482K/L503Q/I506K 11 DSCav1 + ds + replaceexposed (S155C, S290, S190F, V207L) + 513 562 hydrophobic residues(L512C/L513C) + L160K/V178T/L258K/V384T/I431S/L467Q/F477K/L481Q/V482K/L503Q/I506K 12 DSCav1 + cavity filling (S155C, S290,S190F, V207L) + F505W 514 563 13 DSCav1 + cavity filling + replace(S155C, S290, S190F, V207L) + F505W + 515 564 exposed hydrophobicresidues L160K/V178T/L258K/V384T/I431S/L467Q/ 14 DSCav1 + cavityfilling + replace (S155C, S290, S190F, V207L) + F505W + 516 565 exposedhydrophobic residues F477K/L481Q/V482K/L503Q/I506K 15 DSCav1 + cavityfilling + replace (S155C, S290, S190F, V207L) + F505W + 517 566 exposedhydrophobic residues L160K/V178T/L258K/V384T/I431S/L467Q/F477K/L481Q/V482K/L503Q/I506K 16 DSCav1 + ds + cavity filling (S155C,S290, S190F, V207L) + 518 567 L512C/L513C + F505W 17 DSCav1 + ds +cavity filling + replace (S155C, S290, S190F, V207L) + 519 568 exposedhydrophobic residues L512C/L513C + F505W +L160K/V178T/L258K/V384T/I431S/L467Q/ 18 DSCav1 + ds + cavity filling +replace (S155C, S290, S190F, V207L) + 520 569 exposed hydrophobicresidues L512C/L513C + F505W + F477K/L481Q/V482K/L503Q/I506K 19 DSCav1 +ds + cavity filling + replace (S155C, S290, S190F, V207L) + 521 570exposed hydrophobic residues L512C/L513C + F505W +L160K/V178T/L258K/V384T/I431S/L467Q/ F477K/L481Q/V482K/L503Q/I506K 20DSCav1 + Cavity filling + replace (S155C, S290, S190F, V207L) + 522 571exposed hydrophobic residues I506K/S509F/L83F/V90F 21 DSCav1 + Cavityfilling + replace (S155C, S290, S190F, V207L) + 523 572 exposedhydrophobic residues I506K/S509F/L83F/V90F/L230F/L158F 22 DSCav1 +Cavity filling + replace (S155C, S290, S190F, V207L) + 524 573 exposedhydrophobic residues I506K/S509F/F505W/L83F/V90F/L230F/ V185F/T54A 23DSCav1 + Cavity filling (S155C, S290, S190F, V207L) + 525 574L83F/V90F/L230F/I395F 24 DSCav1 + Cavity filling + replace (S155C, S290,S190F, V207L) + 526 575 exposed hydrophobic residuesI506K/S509F/F505W/L83F/V90F/L230F/ L158F/I395F/V185F/T54A 25 DS +S190F + Disulfide stabilization of S190F, S155C, S290C, F488W, L513C,527 576 C-term plus more mutations A514E, I515C 26 DS + S190F + F488W +Disulfide S190F, S155C, S290C, F488W, L513C, 528 577 stabilization ofC-term plus more A514E, G515E, 516C mutations 27 DS + S190F + F488W +Disulfide S190F, S155C, S290C, F488W, L512C, 529 578 stabilization ofC-term plus more L513E, A514C mutations 28 DS + S190F + F488W +Disulfide S190F, S155C, S290C, F488W, L512C, 530 579 stabilization ofC-term plus more L513E, A514E, G515C mutations 29 DS + S190F + F488W +Disulfide S190F, S155C, S290C, A424C, V450C, 531 580 stabilization ofC-term plus more L171C, K191C, F488W, L513C, A514E, mutations plus 2extra intrachain I515C disulfides 30 DS + S190F + F488W + DisulfideS190F, S155C, S290C, A424C, V450C, 532 581 stabilization of C-term plusmore L171C, K191C, F488W, L513C, A514E, mutations plus 2 extraintrachain G515E, 516C disulfides 31 DS + S190F + F488W + DisulfideS190F, S155C, S290C, A424C, V450C, 533 582 stabilization of C-term plusmore L171C, K191C, F488W, L512C, L513E, mutations plus 2 extraintrachain A514C disulfides 32 DS + S190F + F488W + Disulfide S190F,S155C, S290C, A424C, V450C, 534 583 stabilization of C-term plus moreL171C, K191C, F488W, L512C, L513E, mutations plus 2 extra intrachainA514E, G515C disulfides 33 DS + S190F + F488W + Disulfide K77C, I217C,S190F, S155C, S290C, 535 584 stabilization of C-term plus more A424C,V450C, L171C, K191C, F488W, mutations plus 2 extra intrachain disulfideL513C, L514E, A515C and 1 extra interchain disulfide 34 DS + S190F +F488W + Disulfide K77C, I217C, S190F, S155C, S290C, 536 585stabilization of C-term plus more A424C, V450C, L171C, K191C, F488W,mutations plus 2 extra intrachain disulfide L513C, L514E, A515E, G516Cand 1 extra interchain disulfide 35 DS + S190F + F488W + Disulfide K77C,I217C, S190F, S155C, S290C, 537 586 stabilization of C-term plus moreA424C, V450C, L171C, K191C, F488W, mutations plus 2 extra intrachaindisulfide L512C, L513E, A514C and 1 extra interchain disulfide 36 DS +S190F + F488W + Disulfide K77C, I217C, S190F, S155C, S290C, 538 587stabilization of C-term plus more A424C, V450C, L171C, K191C, F488W,mutations plus 2 extra intrachain disulfide L512C, L513E, A514E, G515Cand 1 extra interchain disulfide 37 DS + C-term stabilization cysteinering (S155C, S290C) + L513C, 514E, 515C 539 588 38 DS + C-termstabilization cysteine ring (S155C, S290C) + L513C, 514E, 515E, 540 589516C 39 DS + C-term stabilization cysteine ring (S155C, S290C) + L512C,513E, 514C 541 590 40 DS + C-term stabilization cysteine ring (S155C,S290C) + L512C, 513E, 514E, 542 591 515C 41 DSCav1 + 512/513ds + end atresidue (S155C, S290C, S190F, V207L) + 543 592 513 (L512C/L513C) 42DSCav1 + end at residue 492 (S155C, S290C, S190F, V207L) + 486DEF 544593 to CPC 43 DSCav1 (S155C, S290C, S190F, V207L) 601 44 DSCav1 withC-terminal cavity filling S155C, S290C, S190F, V207L + L512F 672 683mutations 45 DSCav1 with C-terminal cavity filling S155C, S290C, S190F,V207L + 673 684 mutations L513F 46 DSCav1 with C-terminal cavity fillingS155C, S290C, S190F, V207L + L512F, 674 685 mutations L513F 47 DSCav1with C-terminal cavity filling S155C, S290C, S190F, V207L + L512Y, 675686 mutations L513Y 48 DSCav1 with C-terminal cavity filling S155C,S290C, S190F, V207L + L512F, 676 687 mutations L513Y 49 DSCav1 withC-terminal cavity filling S155C, S290C, S190F, V207L + L512W, 677 688mutations L513W 50 DSCav1 with C-terminal cavity filling S155C, S290C,S190F, V207L + L5132W, 678 689 mutations L513Y 51 DSCav1 with C-terminalcavity filling S155C, S290C, S190F, V207L + S509W 679 690 mutations 52DSCav1 with C-terminal cavity filling S155C, S290C, S190F, V207L + 680691 mutations S509F 53 DSCav1 with C-terminal cavity filling S155C,S290C, S190F, V207L + S509W, 681 692 mutations L512F 54 DSCav1 withC-terminal cavity filling S155C, S290C, S190F, V207L + S509W, 682 693mutations L512F, L513F

The SEQ ID NOs listed in Table 8b set forth amino acid sequencesincluding the indicated substitutions, a signal peptide, F2 polypeptide(positions 26-109), a pep27 polypeptide (positions 110-136), a F₁polypeptide (positions 137-513), and a thrombin cleavage site (LVPRGS(positions 547-552 of SEQ ID NO: 185)) and purification tags (his-tag(HHHHHH (positions 553-558 of SEQ ID NO: 185)) and Strep Tag II(SAWSHPQFEK (positions 559-568 of SEQ ID NO: 185))) or a thrombincleavage site (LVPRGS (positions 547-552 of SEQ ID NO: 185)), atrimerization domain (a Foldon domain), and purification tags (his-tag(HHHHHH (positions 553-558 of SEQ ID NO: 185)) and Strep Tag II(SAWSHPQFEK (positions 559-568 of SEQ ID NO: 185))). Thus, in someembodiments, the PreF antigen includes a recombinant RSV F proteinincluding a F₁ polypeptide (e.g., approx. positions 137-513) and a F₂polypeptide (e.g., approx. positions 26-109) as set forth in the SEQ IDNO of one of rows 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34,35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 59, 50, 51, 52,53, or 54 of column 4 (without Foldon domain) or column 5 (withcleavable Foldon domain) of Table 8b.

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a prefusion conformation that includes the aminoacid substitutions listed in one of rows 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11, 12, or 13, of column 3 of Table 8c. The stabilized RSV F protein canbe specifically bound by a prefusion-specific antibody (e.g., D25 orAM22 antibody), and/or includes a RSV F prefusion specific conformation(such as antigenic site Ø).

The SEQ ID NOs listed in Table 8c set forth amino acid sequencesincluding the indicated substitutions, a signal peptide, F₂ polypeptide(positions 26-109), a pep27 polypeptide (positions 110-136), a F₁polypeptide (positions 137-513), a thrombin cleavage site (LVPRGS(positions 547-552 of SEQ ID NO: 185)), and purification tags (his-tag(HHHHHH (positions 553-558 of SEQ ID NO: 185)) and Strep Tag II(SAWSHPQFEK (positions 559-568 of SEQ ID NO: 185))). Thus, in additionalembodiments, the PreF antigen includes a recombinant RSV F proteinincluding a F₁ polypeptide (e.g., approx. positions 137-513) and a F₂polypeptide (e.g., approx. positions 26-109) as set forth in the SEQ IDNO of one of rows 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13 of column4 of Table 8c.

TABLE 8c Exemplary recombinant RSV F protein substitutions and sequencesSEQ ID Description Substitutions NO 1 Cavity filling + replace exposedL503E/I506K/S509F 389 hydrophobic residues 2 Cavity filling + replaceexposed L503E/I506K/S509F/F505W 390 hydrophobic residues 3 Cavityfilling + replace exposed L503E/I506K/S509F/L230F/L158F 394 hydrophobicresidues 4 Interchain disulfide Q279C, S238C 418 5 Cavityfilling/hydrophobic patch Q501F 420 6 cavity filling + replaceE82V/V207M/N227L/V296I 485 hydrophilic 7 cavity filling + replaceE82V/V207I/N227L/V296I 486 hydrophilic 8 cavity filling + prevent helixL158F/Y198F/V207M/S215G/N216P/T219L 491 formation 9 cavity filling +prevent helix L158F/Y198F/V207M/S213G/S215G/T219L 492 formation 10cavity filling + replace V56L/E82V/L203F/V207M/N227L/L230F/V296I 493hydrophilic 11 cavity filling + replaceE82V/L158F/L203F/V207M/N227L/L230F/V296I 494 hydrophilic 12 cavityfilling + replace E82V/L203F/V207M/K226M/N227L/L230F/V296I 495hydrophilic 13 Disulfide + cavity filling L203F/V207I/S180C/S186C/V296I496

b. Membrane Proximal Stabilizing Modifications

In several embodiments, the PreF antigen includes a membrane anchoredform of the recombinant RSV F protein (e.g., with a transmembranedomain). In other embodiments, the PreF antigen includes a soluble formof the recombinant RSV F protein (e.g., without a transmembrane domainor other membrane anchor). It will be understood that there are severaldifferent approaches for generating a soluble or membrane anchoredrecombinant RSV F protein, including those discussed below. Examplesinclude introduction of a trimerization domain, introduction of cysteinepairs that can form a disulfide bond that stabilizes the C-terminalregion of F₁, and introduction of a transmembrane domain (e.g., forapplications including a membrane-anchored PreF antigen).

Further, as disclosed herein, the structure of the RSV F protein incomplex with D25 Fab (i.e., in a prefusion conformation) compared to thestructure of the postfusion RSV F protein (disclosed, e.g., in McLellanet al., J. Virol., 85, 7788, 2011, with coordinates deposited as PDBAccession No. 3 RRR) show structural rearrangements between pre- andpost-fusion conformations in both the membrane-proximal andmembrane-distal lobes. Several embodiments include a modificationtargeted for stabilization of the membrane proximal lobe of the RSV Fprotein prefusion conformation. It will be understood that thesemodifications are not strictly necessary to stabilize a recombinant RSVF protein in a prefusion conformation, but that, in some instances, theyare combined with other prefusion stabilizing modifications, such asthose described above.

i. Trimerization Domain

In several embodiments, the PreF antigen is linked to a trimerizationdomain, for example the PreF antigen can include a recombinant RSV Fprotein including an F1 polypeptide with a trimerization domain linkedto its C-terminus. In some embodiments, the trimerization domainpromotes trimerization of the three F1/F2 monomers in the recombinantRSV F protein. Several exogenous multimerization domains promote stabletrimers of soluble recombinant proteins: the GCN4 leucine zipper(Harbury et al. 1993 Science 262:1401-1407), the trimerization motiffrom the lung surfactant protein (Hoppe et al. 1994 FEBS Lett344:191-195), collagen (McAlinden et al. 2003 J Biol Chem278:42200-42207), and the phage T4 fibritin Foldon (Miroshnikov et al.1998 Protein Eng 11:329-414), any of which can be linked to the F1polypeptide in the PreF antigen to promote trimerization of therecombinant F protein, as long as the PreF antigen is specifically boundby a prefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ).

In some examples, the PreF antigen can be linked to a GCN4 leucinezipper domain, for example the PreF antigen can include a recombinantRSV F protein including an F1 polypeptide with a GCN4 leucine zipperdomain linked to its C-terminus. In specific examples, GCN4 leucinezipper domain is provided in the CSGJ series of constructs describedherein.

In some examples, the PreF antigen can be linked to a Foldon domain, forexample, the PreF antigen can include a recombinant RSV F proteinincluding an F1 polypeptide with a Foldon domain linked to itsC-terminus. In specific examples, the Foldon domain is a T4 fibritinFoldon domain such as the amino acid sequence GYIPEAPRDGQAYVRKDGEWVLLSTF(SEQ ID NO: 351), which adopts a β-propeller conformation, and can foldand trimerize in an autonomous way (Tao et al. 1997 Structure5:789-798).

In some specific examples, the PreF antigen includes a recombinant RSV Fprotein linked to a T4 fibritin Foldon domain, includes a F₂ polypeptideand an F₁ polypeptide linked to a Foldon domain as set forth in one ofSEQ ID NOs: 185, 189-303, or 371-376. Typically, the heterologousmultimerization motif is positioned C-terminal to the F₁ domain.Optionally, the multimerization domain is connected to the F₁polypeptide via a linker, such as an amino acid linker, such as thesequence GG. The linker can also be a longer linker (for example,including the sequence GG, such as the amino acid sequence: GGSGGSGGS;SEQ ID NO: 352). Numerous conformationally neutral linkers are known inthe art that can be used in this context without disrupting theconformation of the PreF antigen. Some embodiments include a proteasecleavage site for removing the Foldon domain from the F1 polypeptide,such as, but not limited to, a thrombin site between the F1 polypeptideand the Foldon domain.

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including any of the trimerization domain modifications listedabove combined with any of the modifications listed in section II.B.1.a.For example, in some embodiments, the PreF antigen includes arecombinant RSV F protein including any of the trimerization domainmodifications listed above in combination with one or more of thedisulfide bond modification listed in one of rows 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43,44, 45, 46, 47, 48, 49, 50, or 51 of Table 5, and/or one or more of thecavity filling modifications listed in one of rows 1, 2, 3, 4, 5, 6, 7,or 8 of Table 6, and/or one or more of the repacking modificationslisted in one of rows 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, or 47 of Table 7,and/or one or more of the glycosylation modifications listed in one orrows 1, 2, 3, 4, 5, 6, 7, 8, or 9 of Table 8, wherein the PreF antigenis specifically bound by a prefusion-specific antibody (e.g., D25 orAM22 antibody), and/or includes a RSV F prefusion specific conformation(such as antigenic site Ø).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including any of the trimerization domain modifications listedabove linked to an F1 polypeptide including a disulfide bond between apair of cysteines at positions 155 and 290, and a cavity-filling aminoacid substitution at position 190; or a disulfide bond between a pair ofcysteines at positions 155 and 290, a cavity-filling amino acidsubstitution at position 190, and a cavity-filling amino acidsubstitution at position 207.

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including any of the trimerization domain modifications listedabove linked to an F1 polypeptide including S155C, S290C, and S190Famino acid substitutions, S155C, S290C, and S190W amino acidsubstitutions, or S155C, S290C, and S190L amino acid substitutions. Infurther embodiments, the PreF antigen includes a recombinant RSV Fprotein including any of the trimerization domain modifications listedabove linked to an F1 polypeptide including S155C, S290C, S190F, andV207L amino acid substitutions, S155C, S290C, S190W, and V207L aminoacid substitutions, S155C, S290C, S190L, and V207L amino acidsubstitutions, S155C, S290C, S190F, and V207F amino acid substitutions,S155C, S290C, S190W, and V207F amino acid substitutions, S155C, S290C,S190L, and V207F amino acid substitutions, S155C, S290C, S190F, andV207W amino acid substitutions, S155C, S290C, S190W, and V207W aminoacid substitutions, or S155C, S290C, S190L, and V207W amino acidsubstitutions.

For example, in some embodiments, the PreF antigen includes arecombinant RSV F protein stabilized in a RSV F protein prefusionconformation, wherein the F₂ polypeptide and the F₁ polypeptide linkedto the foldon domain include the amino acid sequence set forth aspositions 26-109 and 137-544, respectively, of any one of SEQ ID NO:185, SEQ ID NO: 189, SEQ ID NO: 201, SEQ ID NO: 202, SEQ ID NO: 205, SEQID NO: 207, SEQ ID NO: 209, SEQ ID NO: 213, SEQ ID NO: 244, SEQ ID NO:245, SEQ ID NO: 247, SEQ ID NO: 257, SEQ ID NO: 264, SEQ ID NO: 265, SEQID NO: 266, SEQ ID NO: 267, SEQ ID NO: 268, SEQ ID NO: 269, SEQ ID NO:270, SEQ ID NO: 271, SEQ ID NO: 272, SEQ ID NO: 273, SEQ ID NO: 274, SEQID NO: 275, SEQ ID NO: 277, SEQ ID NO: 278, SEQ ID NO: 279, SEQ ID NO:280, SEQ ID NO: 281, SEQ ID NO: 282, SEQ ID NO: 284, SEQ ID NO: 302, SEQID NO: 303, SEQ ID NO: 190, SEQ ID NO: 211, SEQ ID NO: 212, SEQ ID NO:243, SEQ ID NO: 246, SEQ ID NO: 276, SEQ ID NO: 283, SEQ ID NO: 285, orSEQ ID NO: 263; or positions 26-109 and 137-545, respectively, of anyone of SEQ ID NO: 258, SEQ ID NO: 259, SEQ ID NO: 260, SEQ ID NO: 261,SEQ ID NO: 262, SEQ ID NO: 296, SEQ ID NO: 297, SEQ ID NO: 298, or SEQID NO: 299, wherein the PreF antigen is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a RSV F protein prefusion conformation, whereinthe F₂ polypeptide and the F₁ polypeptide linked to the foldon domaininclude the amino acid sequence set forth as positions 26-109 and137-544, respectively, of any one of SEQ ID NO: 371 (RSV A with S155C,S290C, S190F and V207L substitutions), SEQ ID NO: 372 (RSV B with S155C,S290C, S190F and V207L substitutions), SEQ ID NO: 373 (bovine RSV withS155C, S290C, S190F and V207L substitutions), SEQ ID NO: 374 (RSV A withS155C, S290C, and S190F substitutions), SEQ ID NO: 375 (RSV B withS155C, S290C, and S190F substitutions); or SEQ ID NO: 376 (bovine RSVwith S155C, S290C, and S190F substitutions), wherein the PreF antigen isspecifically bound by a prefusion-specific antibody (e.g., D25 or AM22antibody), and/or includes a RSV F prefusion specific conformation (suchas antigenic site Ø).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including a F₁ polypeptide and a F₂ polypeptide from a human RSVA subtype, a human RSV B subtype, or a bovine RSV, wherein the F₁polypeptide is linked to any of the trimerization domain modificationslisted above, and the F1 polypeptide further includes any of thestabilizing modifications described herein (e.g., one of the abovecombinations of stabilizing substitutions such as S155C, S290C, andS190F substitutions, or S155C, S290C, S190F, and V207L substitutions).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a RSV F protein prefusion conformation, andincludes one or more cavity-filling amino acid substitution and a Foldondomain, wherein the F₂ polypeptide and the F₁ polypeptide linked to theFoldon domain include the amino acid sequence set forth as positions26-109 and 137-544, respectively, of any one of SEQ ID NO: 191, SEQ IDNO: 193, SEQ ID NO: 196, SEQ ID NO: 197, SEQ ID NO: 248, SEQ ID NO: 192,SEQ ID NO: 195, or SEQ ID NO: 194; wherein the PreF antigen isspecifically bound by a prefusion-specific antibody (e.g., D25 or AM22antibody), and/or includes a RSV F prefusion specific conformation (suchas antigenic site Ø).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a RSV F protein prefusion conformation, andincludes one or more repacking amino acid substitutions and a foldondomain, wherein the F₂ polypeptide and the F₁ polypeptide linked to thefoldon domain include the amino acid sequence set forth as positions26-109 and 137-544, respectively, of any one of SEQ ID NO: 249, SEQ IDNO: 250, SEQ ID NO: 251, SEQ ID NO: 252, SEQ ID NO: 253, SEQ ID NO: 254,SEQ ID NO: 255, SEQ ID NO: 256, SEQ ID NO: 288, SEQ ID NO: 289, SEQ IDNO: 290, SEQ ID NO: 291, SEQ ID NO: 292, SEQ ID NO: 293, SEQ ID NO: 294,SEQ ID NO: 295, SEQ ID NO: 296, SEQ ID NO: 297, SEQ ID NO: 326, SEQ IDNO: 327, SEQ ID NO: 328, SEQ ID NO: 329, SEQ ID NO: 330, SEQ ID NO: 331,SEQ ID NO: 332, SEQ ID NO: 333, SEQ ID NO: 334, SEQ ID NO: 335, SEQ IDNO: 336, or SEQ ID NO: 337; wherein the PreF antigen is specificallybound by a prefusion-specific antibody (e.g., D25 or AM22 antibody),and/or includes a RSV F prefusion specific conformation (such asantigenic site Ø).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a RSV F protein prefusion conformation, andincludes one or more N-linked glycosylation sites and a Foldon domain,wherein the F₂ polypeptide and the F₁ polypeptide linked to the Foldondomain include the amino acid sequence set forth as positions 26-109 and137-544, respectively, of any one of SEQ ID NOs selected from the groupconsisting of SEQ ID NO: 198, SEQ ID NO: 199, SEQ ID NO: 200, SEQ ID NO:203, SEQ ID NO: 204, SEQ ID NO: 214, SEQ ID NO: 215, SEQ ID NO: 216, orSEQ ID NO: 217; wherein the PreF antigen is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including the amino acid substitutions listed in one of row 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 of column 3 ofTable 5b, wherein the F1 polypeptide of the recombinant RSV F protein islinked to a Foldon domain. Some embodiments include a protease cleavagesite for removing the Foldon domain from the F1 polypeptide, for examplea thrombin cleavage site.

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a RSV F protein prefusion conformation, includinga F₂ polypeptide and a F₁ polypeptide linked to a Foldon domain, whereinthe F₂ polypeptide and the F₁ polypeptide linked to the Foldon domaininclude the amino acid sequence set forth as positions 26-109 and137-544, respectively, of one of the SEQ ID NOs listed in one of row 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 of column 4 ofTable 5b. In several embodiments, the F₁ polypeptide linked to theFoldon domain further includes a protease cleavage site, such as, butnot limited to, a thrombin site, between the F1 polypeptide and theFoldon domain.

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including the amino acid substitutions listed in one of row 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39,40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57,58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75,76, 77, 78, 79, 80, 81, 82, 83, or 84 of column 3 of Table 6b, whereinthe F1 polypeptide of the recombinant RSV F protein is linked to aFoldon domain.

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a RSV F protein prefusion conformation, includinga F₂ polypeptide and a F₁ polypeptide linked to a Foldon domain, whereinthe F₂ polypeptide and the F₁ polypeptide linked to the Foldon domaininclude the amino acid sequence set forth as positions 26-109 and137-544, respectively, of one of the SEQ ID NOs listed in one of row 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39,40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57,58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75,76, 77, 78, 79, 80, 81, 82, 83, or 84 of column 4 of Table 6b.

In further embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a RSV F protein prefusion conformation, whereinthe recombinant RSV F protein includes the amino acid substitutionslisted in one of row 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 59, 50, 51,52, 53, or 54 of column 3 of Table 8b, wherein the F1 polypeptide of therecombinant RSV F protein is linked to a Foldon domain. In someembodiments, the PreF antigen includes a recombinant RSV F proteinstabilized in a RSV F protein prefusion conformation, including a F₂polypeptide and a F₁ polypeptide linked to a Foldon domain, wherein theF₂ polypeptide and the F₁ polypeptide linked to the Foldon domaininclude the amino acid sequence set forth as positions 26-109 and137-544, respectively, of one of the SEQ ID NOs listed in one of row 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39,40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, or 54 of column5 of Table 8b. These sequences include a thrombin cleavage site betweenthe F1 polypeptide and the Foldon domain.

In further embodiments, the PreF antigen includes a recombinant RSV Fprotein stabilized in a RSV F protein prefusion conformation, whereinthe recombinant RSV F protein includes the amino acid substitutionslisted in row 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13 of column 3of Table 8c, wherein the F1 polypeptide of the recombinant RSV F proteinis linked to a Foldon domain. In some embodiments, the PreF antigenincludes a recombinant RSV F protein stabilized in a RSV F proteinprefusion conformation, including a F₂ polypeptide and a F₁ polypeptidelinked to a Foldon domain, wherein the F₂ polypeptide and the F₁polypeptide linked to the Foldon domain include the amino acid sequenceset forth as positions 26-109 and 137-544, respectively, of the SEQ IDNO listed in row 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13 of column4 of Table 8c.

Modified Foldon domains can also be used, such as a Foldon domainincluding an amino acid sequence set forth as GYIPEAPRDGQCYVRCDGEWVLLSTF(SEQ ID NO: 694), GYIPECPRDGQAYVCKDGEWVLLSTF (SEQ ID NO: 695),GYIPEAPRDGQCYCRKDGEWVLLSTF (SEQ ID NO: 696), orGYIPEAPRDGQACVRKDGECVLLSTF (SEQ ID NO: 697). These modified Foldondomains include amino acid substitutions that add two cysteine residuesfor formation of stabilizing disulfide bonds. Exemplary RSV F proteinsequences including the DSCav1 amino acid substitutions linked to themodified Foldon domains include those set forth as SEQ ID NO: 651, SEQID NO: 652, SEQ ID NO: 653, and SEQ ID NO: 654. In some embodiments, anyof the disclosed recombinant RSV F proteins can be linked to a modifiedFoldon domain as described herein.

ii. Disulfide Bonds

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including a F1 polypeptide including one or more disulfide bondsthat are used to stabilize the membrane proximal lobe of the recombinantRSV F protein. The cysteine residues that form the disulfide bond can beintroduced into the recombinant RSV F protein by one or more amino acidsubstitutions.

The location of the cysteine (or cysteines) of a disulfide bond tostabilize the membrane proximal lobe of the RSV F protein in a prefusionconformation can readily be determined by the person of ordinary skillin the art using methods described herein and familiar to the skilledartisan. In some embodiments, a ring of disulfide bonds is introducedinto the C-terminus of the F1 polypeptide by substituting cysteineresidues for amino acids of the α10 helix. The three α10 helixes of theRSV F Ectodomain for a coil-coil that stabilized the membrane proximalportion of the protein. When expressed in cells, inter-protomerdisulfide bonds form between the cysteines introduced into the α10helix, thereby “locking” the three α10 helix's in close proximity andpreventing movement of the membrane proximal domain from the pre- to thepost-fusion conformation. The α10 helix of the RSV F protein includesresidues 492 to the transmembrane domain (residue 529).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including a disulfide bond between cysteine residues located atRSV F positions 486 and 487, or between cysteine residues located at RSVF positions 512 and 513, wherein the PreF antigen is specifically boundby a prefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ). In some such embodiments, the F₁ polypeptide includes D486C andE487C substitutions, L512C and L513C substitutions, or D486C, E487C,L512C, and L513C substitutions respectively.

In some embodiments, amino acids can be inserted (or deleted) from the Fprotein sequence to adjust the alignment of residues in the F proteinstructure, such that particular residue pairs are within a sufficientlyclose distance to form an disulfide bond. In some such embodiments, thePreF antigen includes a recombinant RSV F protein including a disulfidebond between cysteine residues located at 486 and 487; with a prolineinsertion between positions 486 and 487, wherein the PreF antigen isspecifically bound by a prefusion-specific antibody (e.g., D25 or AM22antibody), and/or includes a RSV F prefusion specific conformation (suchas antigenic site Ø). In some such embodiments, the F₁ polypeptideincludes D486C and E487C substitutions, and a proline insertion betweenpositions 486 and 487.

In additional embodiments, the PreF antigen includes a recombinant RSV Fprotein including a disulfide bond between a cysteine residue located atposition 493 and a cysteine residue inserted between positions 329 and330, wherein the PreF antigen is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ). In some such embodiments, the F₁ polypeptide includes S493Csubstitution, and a cysteine residue inserted between positions 329 and330.

In additional embodiments, the PreF antigen includes a recombinant RSV Fprotein including a disulfide bond between a cysteine residue located atposition 493 and a cysteine residue inserted between positions 329 and330, and further includes a glycine insertion between residues 492 and493, wherein the PreF antigen is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ). In some such embodiments, the F₁ polypeptide includes S493Csubstitution, a cysteine residue inserted between positions 329 and 330,and a glycine insertion between residues 492 and 493

In additional embodiments, the recombinant RSV F protein includescysteine substitutions in the (10 helix at positions 525 and 526, 512and 513, and/or 519 and 520, which can form interprotomer disulfidebonds to stabilize the C-terminal region of the F1 polypeptide. Forexample, in some embodiments, the recombinant RSV F protein includes anyof the “motifs” listed in Table 23. In additional embodiments, therecombinant RSV F protein includes an amino acid sequence at least 80%(such as at least 90%, at least 95% or at least 98% identical) to theamino acid sequence set forth as any one of SEQ ID NOs: 829-1025 or1456-1468, optionally without including the purification tags ortrimerization domains included in these sequences.

In some embodiments, the recombinant RSV F protein includes, extendingC-terminal from position 512, the amino acid sequence set forth as oneof CCHNVNAGKSTTN (residues 512-524 of SEQ ID NO: 844) or CCHNVNACCSTTN(residues 512-524 of SEQ ID NO: 853); or CCHNVNACCSTTNICCTT (residues512-529 of SEQ ID NO: 853).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including any of the above disulfide bond modifications forstabilizing the membrane proximal lobe of the RSV F protein, combinedwith any of the stabilization modifications listed in section II.B.1.a.In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including any of the disulfide bond modifications forstabilizing the membrane proximal lobe of the RSV F protein listed abovein combination with the disulfide bond substitutions listed in one ofrow 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37,38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, or 51 of Table 5, orrow 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16 of Table 5b,or the cavity filling substitutions listed in one of row 1, 2, 3, 4, 5,6, 7, or 8 of Table 6, or one of row 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65,66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83or 84 of column 3 of Table 6b, or the repacking substitutions listed inone of row 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, or 47 of Table 7, or theglycosylation modifications listed in one of row 1, 2, 3, 4, 5, 6, 7, 8,or 9 of Table 8, or the substitutions listed in row 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43,44, 45, 46, 47, 48, 59, 50, 51, 52, 53, or 54 of column 3 of Table 8b,or the substitutions listed in row 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,12, or 13 of column 3 of Table 8c, wherein the PreF antigen isspecifically bound by a prefusion-specific antibody (e.g., D25 or AM22antibody), and/or includes a RSV F prefusion specific conformation (suchas antigenic site Ø).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including any of the disulfide bond modifications forstabilizing the membrane proximal lobe of the RSV F protein listed aboveand further includes a F1 polypeptide including a disulfide bond betweena pair of cysteines at positions 155 and 290, and a cavity-filling aminoacid substitution at position 190; or a disulfide bond between a pair ofcysteines at positions 155 and 290, a cavity-filling amino acidsubstitution at position 190, and a cavity-filling amino acidsubstitution at position 207.

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including any of the disulfide bond modifications forstabilizing the membrane proximal lobe of the RSV F protein listed aboveand further includes a F1 polypeptide including S155C, S290C, and S190Famino acid substitutions, S155C, S290C, and S190W amino acidsubstitutions, or S155C, S290C, and S190L amino acid substitutions. Infurther embodiments, the PreF antigen includes a recombinant RSV Fprotein including any of the disulfide bond modifications forstabilizing the membrane proximal lobe of the RSV F protein listed aboveand further includes a F1 polypeptide including S155C, S290C, S190F, andV207L amino acid substitutions, S155C, S290C, S190W, and V207L aminoacid substitutions, S155C, S290C, S190L, and V207L amino acidsubstitutions, S155C, S290C, S190F, and V207F amino acid substitutions,S155C, S290C, S190W, and V207F amino acid substitutions, S155C, S290C,S190L, and V207F amino acid substitutions, S155C, S290C, S190F, andV207W amino acid substitutions, S155C, S290C, S190W, and V207W aminoacid substitutions, or S155C, S290C, S190L, and V207W amino acidsubstitutions.

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including a F₂ polypeptide and a F₁ polypeptide including theamino acid sequence set forth as positions 26-109 and 137-513,respectively, of any one of SEQ ID NO: 371 (RSV A with S155C, S290C,S190F and V207L substitutions), SEQ ID NO: 372 (RSV B with S155C, S290C,S190F and V207L substitutions), SEQ ID NO: 373 (bovine RSV with S155C,S290C, S190F and V207L substitutions), SEQ ID NO: 374 (RSV A with S155C,S290C, and S190F substitutions), SEQ ID NO: 375 (RSV B with S155C,S290C, and S190F substitutions); or SEQ ID NO: 376 (bovine RSV withS155C, S290C, and S190F substitutions), wherein the recombinant RSV Fprotein further includes any of the disulfide bond modifications forstabilizing the membrane proximal lobe of the RSV F protein listedabove, wherein the PreF antigen is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ).

In several embodiments, the PreF antigen includes a recombinant RSV Fprotein including a F₁ polypeptide and a F₂ polypeptide from a human RSVA subtype, a human RSV B subtype, or a bovine RSV, wherein therecombinant RSV F protein further includes any of the disulfide bondmodifications for stabilizing the membrane proximal lobe of the RSV Fprotein listed above, and wherein the F1 polypeptide further includesany of the stabilizing modifications described herein (e.g., one of theabove combinations of stabilizing substitutions such as S155C, S290C,and S190F substitutions, or S155C, S290C, S190F, and V207Lsubstitutions).

iii. Transmembrane Domains

In some embodiments, the recombinant RSV F protein includes atransmembrane domain linked to the F₁ polypeptide, for example, for anapplication including a membrane anchored PreF antigen). For example,the presence of the transmembrane sequences is useful for expression asa transmembrane protein for membrane vesicle preparation. Thetransmembrane domain can be linked to a F₁ protein containing any of thestabilizing mutations provided herein, for example, those describedabove, such as a F₁ protein with a S155C/S290C cysteine substitution.Additionally, the transmembrane domain can be further linked to a RSV F₁cytosolic tail. Examples including a signal peptide, F₂ polypeptide(positions 26-109), pep27 polypeptide (positions 110-136), F₁polypeptide (positions 137-513), a RSV transmembrane domain are providedas SEQ ID NO: 323 (without a cytosolic domain) and SEQ ID NO: 324 (witha cytosolic domain).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including an F1 polypeptide linked to a transmembrane domain,combined with any of the stabilization modifications listed in sectionII.B.1a. For example, in some embodiments, the PreF antigen includes arecombinant RSV F protein including an F1 polypeptide linked to atransmembrane domain, and further includes the disulfide bondsubstitutions listed in one of row 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,48, 49, 50, or 51 of Table 5, or row 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,12, 13, 14, 15 or 16 of Table 5b, or the cavity filling substitutionslisted in one of row 1, 2, 3, 4, 5, 6, 7, or 8 of Table 6, or one of row1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56,57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74,75, 76, 77, 78, 79, 80, 81, 82, 83 or 84 of column 3 of Table 6b, or therepacking substitutions listed in one of row 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27,28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45,46, or 47 of Table 7, or the glycosylation modifications listed in oneof row 1, 2, 3, 4, 5, 6, 7, 8, or 9 of Table 8, or the substitutionslisted in row 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 59, 50, 51, 52, 53,or 54 of column 3 of Table 8b, or the substitutions listed in row 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13 of column 3 of Table 8c, whereinthe PreF antigen is specifically bound by a prefusion-specific antibody(e.g., D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø).

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including an F1 polypeptide linked to a transmembrane domain,wherein the F1 polypeptide further includes a disulfide bond between apair of cysteines at positions 155 and 290, and a cavity-filling aminoacid substitution at position 190; or a disulfide bond between a pair ofcysteines at positions 155 and 290, a cavity-filling amino acidsubstitution at position 190, and a cavity-filling amino acidsubstitution at position 207.

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including an F1 polypeptide linked to a transmembrane domain,wherein the F1 polypeptide further includes S155C, S290C, and S190Famino acid substitutions, S155C, S290C, and S190W amino acidsubstitutions, or S155C, S290C, and S190L amino acid substitutions. Infurther embodiments, the PreF antigen includes a recombinant RSV Fprotein including an F1 polypeptide linked to a transmembrane domain,wherein the F1 polypeptide further includes S155C, S290C, S190F, andV207L amino acid substitutions, S155C, S290C, S190W, and V207L aminoacid substitutions, S155C, S290C, S190L, and V207L amino acidsubstitutions, S155C, S290C, S190F, and V207F amino acid substitutions,S155C, S290C, S190W, and V207F amino acid substitutions, S155C, S290C,S190L, and V207F amino acid substitutions, S155C, S290C, S190F, andV207W amino acid substitutions, S155C, S290C, S190W, and V207W aminoacid substitutions, or S155C, S290C, S190L, and V207W amino acidsubstitutions.

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including a F₂ polypeptide and a F1 polypeptide linked to atransmembrane domain, wherein the F₂ polypeptide and the F₁ polypeptidelinked to the transmembrane domain include the amino acid sequence setforth as positions 26-109 and 137-513, respectively, of any one of SEQID NO: 371 (RSV A with S155C, S290C, S190F and V207L substitutions), SEQID NO: 372 (RSV B with S155C, S290C, S190F and V207L substitutions), SEQID NO: 373 (bovine RSV with S155C, S290C, S190F and V207Lsubstitutions), SEQ ID NO: 374 (RSV A with S155C, S290C, and S190Fsubstitutions), SEQ ID NO: 375 (RSV B with S155C, S290C, and S190Fsubstitutions); or SEQ ID NO: 376 (bovine RSV with S155C, S290C, andS190F substitutions), wherein the PreF antigen is specifically bound bya prefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ).

In several embodiments, the PreF antigen includes a recombinant RSV Fprotein including a F₁ polypeptide and a F₂ polypeptide from a human RSVA subtype, a human RSV B subtype, or a bovine RSV, wherein the F₁polypeptide is linked to any of the transmembrane domains listed above,and the F1 polypeptide further includes any of the stabilizingmodifications described herein (e.g., one of the above combinations ofstabilizing substitutions such as S155C, S290C, and S190F substitutions,or S155C, S290C, S190F, and V207L substitutions).

iv. Cavity Filling Substitutions

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein including a F1 polypeptide including one or more cavity fillingsubstitutions that are used to stabilize the membrane proximal lobe ofthe recombinant RSV F protein. In some embodiments, the PreF antigenincludes a recombinant RSV F protein including a F1 polypeptide withV207L and L512F; L513F; L512F and L513F; L512Y and L513Y; L512F andL513Y; L512W and L513W; L5132W and L513Y; S509W; S509F; S509W and L512F;or S509W, L512F and L513F substitutions, wherein the PreF antigen isspecifically bound by a prefusion-specific antibody (e.g., D25 or AM22antibody), and/or includes a RSV F prefusion specific conformation (suchas antigenic site Ø). Exemplary sequences with such substitutionsinclude SEQ ID NOs: 672-682.

c. Antigenic Sites

In some embodiments, the PreF antigen includes a recombinant RSV Fprotein that is stabilized in a prefusion conformation and includesfurther modification to eliminate a known antigenic site other thanantigenic site Ø. For example, the recombinant RSV F protein can includea modification that disrupts antigenic site I, II or IV. Suchmodifications can be identified, for example, by binding of antibodiesspecific for these sites.

In some embodiments, the antigens are provided that include arecombinant RSV F protein that includes modification to eliminateantigenic site Ø. Such antigens are useful, for example, as controlreagents.

Exemplary modifications for removing antigenic site Ø and/or antigenicsite II are listed in Table 8c1.

TABLE 8c1 Exemplary recombinant RSV F protein substitutions andsequences Description Substitutions SEQ ID NO 1 knock out site Ø bindingK65N/N67T, P205N/V207T, K209N/S211T + Avi-tag 655 2 knock out site IIbinding Q270T + Avi-tag 656 3 knock out site II binding N268R/K272E +Avitag 657 4 knock out site Ø binding K65N/N67T, P205N/V207T,K209N/S211T + Avi-tag 658 5 knock out site II binding Q270T + Avi-tag659 6 knock out site II binding N268R/K272E + Avitag 660 7 knock outsite Ø and II K65N/N67T, P205N/V207T, K209N/S211T, Q270T + Avi- 661binding tag 8 knock out site Ø and II K65N/N67T, P205N/V207T, 662binding K209N/S211T, N268R/K272E + Avi-tag 9 knock out site Ø and IIK65N/N67T, P205N/V207T, K209N/S211T, Q270T + Avi- 663 binding tag 10knock out site Ø and II K65N/N67T, P205N/V207T, 664 binding K209N/S211T,N268R/K272E + Avi-tag

d. Single Chain RSV F Proteins

In some embodiments, the recombinant RSV F protein is a single chain RSVF protein, which includes a single polypeptide chain including the RSVF₁ polypeptide and the RSV F₂ polypeptide. The disclosed single chainRSV F proteins do not include the furin cleavage sites flanking thepep27 polypeptide of RSV F protein; therefore, when produced in cells,the F polypeptide is not cleaved into separate F1 and F2 polypeptides.In several embodiments, the remaining portions of the F₁ and F₂polypeptides are joined by a linker, such as a peptide linker.

In several embodiments, a single polypeptide chain including the F₂,pep27, and F₁ sequences is produced. The single chain RSV F proteins caninclude the pep27 sequence, or this sequence can be deleted. Further, inexamples wherein the pep27 sequence is deleted, a linker (such as apeptide linker) optionally can be placed between the F₂ and F₁polypeptides in the recombinant single chain RSV F protein. In someembodiments, a single chain RSV F protein includes deletion of RSV Fpositions 98-149 or 106-149 which removes the two furin cleavage sites,the pep27 polypeptide, and the fusion peptide. In some embodiments, asingle chain RSV F protein includes deletion of RSV F positions 98-136,98-144, 98-149, 106-136, 104-144, or 106-144.

In several embodiments, the stabilizing mutations disclosed herein (forexample, in sections (B.1.a) through (B.1.c) above can be included inthe single chain RSV F protein. For example, in some embodiments, thesingle chain RSV F protein include S155C and S290C substitutions; S155C,S290C and S190F substitutions, or S155C, S290C, S190F, and V207Lsubstitutions. In some embodiments, the PreF antigen includes arecombinant RSV F protein in single chain format stabilized in aprefusion conformation that includes the amino acid substitutions listedin one of rows 1, 2, 3, 4, 5, 6, or 7 of column 3 of Table 8d. Thestabilized RSV F protein can be specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ).

Exemplary sequences are listed in Table 8d. The SEQ ID NOs listed inTable 8d set forth amino acid sequences including the indicatedsubstitutions, a signal peptide, F₂ polypeptide (positions 26-109), apep27 polypeptide (positions 110-136), a F₁ polypeptide (positions137-513), and a thrombin cleavage site (LVPRGS (positions 547-552 of SEQID NO: 185)) and purification tags (his-tag (HHHHHH (positions 553-558of SEQ ID NO: 185)) and Strep Tag II (SAWSHPQFEK (positions 559-568 ofSEQ ID NO: 185))) or a thrombin cleavage site (LVPRGS (positions 547-552of SEQ ID NO: 185)), a trimerization domain (a Foldon domain), andpurification tags (his-tag (HHHHHH (positions 553-558 of SEQ ID NO:185)) and Strep Tag II (SAWSHPQFEK (positions 559-568 of SEQ ID NO:185))). Thus, in additional embodiments, the PreF antigen includes arecombinant RSV F protein including a F₁ polypeptide (e.g., approx.positions 137-513) and a F2 polypeptide (e.g., approx. positions 26-109)as set forth in the SEQ ID NO listed in of one of rows 1, 2, 3, 4, 5, 6,7, 8, 9, 10, 11, 12, 13, or 14 of column 4 (without Foldon domain) orcolumn 5 (with cleavable Foldon domain) of Table 8d. Additionalexemplary single chain RSV F protein mutations and sequences aredescribed herein, for example as disclosed in Table 8e (e.g., rows34-43) and Table 18.

TABLE 8d Single chain recombinant RSV F proteins With Without Thrombin-Foldon Cleavable domain Foldon SEQ ID domain SEQ Description MutationsNO ID NO 1 Single chain DS S155C, S290C 545 594 2 Single chain Cav1S190F, V207L 546 595 3 Single chain F488W F488W 547 596 4 Single chainDSCav1 (S155C, S290, S190F, V207L) 548 597 5 Single chain DS + F488W(S155C, S290C) + F488W 549 598 6 Single chain Cav1 + F488W (S190F,V207L) + F488W 550 599 7 Single chain DSCav1 + F488W (S155C, S290,S190F, V207L) + 551 600 F488W 8 add cav1 to SEQ ID NO: 320 add cav1 toSEQ ID NO: 320 665 single chain single chain 9 add cav1, F488W to SEQ IDadd cav1, F488W to SEQ ID 666 NO: 320] single chain NO: 320] singlechain 10 add cav1 to SEQ ID NO: 319 add cav1 to SEQ ID NO: 319 667single chain single chain 11 add cav1 F488W to SEQ ID NO: add cav1 F488Wto SEQ ID 668 319 single chain NO: 319 single chain 12 single chain withimproved 155C, S290C, S190F, V207L, 669 (not a linker GS linker between105/145 cleavable Foldon) 13 single chain with improved 155C, S290C, GSlinker 670 linker between residue 105 to 145 14 single chain withimproved 155C, S290C, GS linker 671 linker between residue 105 to 145Sequences of additional single chain RSV f proteins that are stabilizedin a prefusion confirmation are provided in Table 19, including singlechain RSV F proteins with non-cleavable Foldon domains, cleavable Foldondomains, and linked to protein nanoparticle subunits.

2. Minimal Site Ø Immunogens

The site Ø epitope of RSV F is located on the apex of the trimer spikeand includes the region recognized by the three neutralizing antibodiesD25, AM22 and 5C4. More specifically, as delineated by the crystalstructure of the RSV F/D25 complex, this epitope comprises the outersurface of helix α4 (residues 196-209) and the adjacent loop (residues63-68) between β2 and α1. Provided herein are immunogens that includethese minimal aspects of the RSV F protein and which are useful, forexample, for inducing an immune response to RSV, and also for specificbinding to RSV F protein antibodies, for example as probes to identifyor detect such antibodies.

Accordingly, in some embodiments, the recombinant RSV F protein includesthe minimal region necessary to stimulate an immune response to RSV. Insome embodiments, the RSV F protein includes or consists of an aminoacid sequence at least 80% identical to a sequence set forth in Table20. In additional embodiments, the recombinant RSV F protein comprisescircular permutation of antigenic site Ø as set forth in Table 20, suchas as set forth in SEQ ID NOs: 1027-1052.

The minimal epitope region can be linked to a scaffold protein tostabilize the epitope in an antigenic conformation. For example, any ofthe minimal site Ø antigen listed herein can be linked to a 2KNO, 2A90,2W59, 3U2E, 2VJ1, 1CHD, 1PQZ, or a 2MOE scaffold protein. These are thereference identifiers for specific sequences located in the PDBdatabase, and are incorporated by reference herein as present in thedata base on Mar. 11, 2014. Specific examples of minimal site Ø antigenlinked to a scaffold protein are provided herein in Table 20.

Any of the minimal site Ø antigen can be linked to a proteinnanoparticle subunit, for example a ferritin subunit or a lumazinesynthase subunit, to generate a protein nanoparticle. Specific examplesof minimal site Ø antigens linked to a protein nanoparticle subunit areprovided herein in the Table 21.

In several embodiments, the PreF antigen includes an epitope-scaffoldprotein including a RSV F protein prefusion specific epitope in aprefusion specific conformation. In some examples, the epitope scaffoldprotein includes any of the recombinant RSV F proteins stabilized in aprefusion conformation as disclosed herein. The prefusion specificepitope can be placed anywhere in the scaffold protein (for example, onthe N-terminus, C-terminus, or an internal loop), as long as the PreFantigen including the epitope scaffold protein is specifically bound bya prefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ).

Methods for identifying and selecting scaffolds are disclosed herein andknown to the person of ordinary skill in the art. For example, methodsfor superposition, grafting and de novo design of epitope-scaffolds aredisclosed in U.S. Patent Application Publication No. 2010/0068217,incorporated by reference herein in its entirety.

“Superposition” epitope-scaffolds are based on scaffold proteins havingan exposed segment with similar conformation as the target epitope—thebackbone atoms in this “superposition-region” can be structurallysuperposed onto the target epitope with minimal root mean squaredeviation (RMSD) of their coordinates. Suitable scaffolds are identifiedby computationally searching through a library of protein crystalstructures; epitope-scaffolds are designed by putting the epitoperesidues in the superposition region and making additional mutations onthe surrounding surface of the scaffold to prevent clash or otherinteractions with the antibody.

“Grafting” epitope-scaffolds utilize scaffold proteins that canaccommodate replacement of an exposed segment with the crystallizedconformation of the target epitope. For each suitable scaffoldidentified by computationally searching through all protein crystalstructures, an exposed segment is replaced by the target epitope and thesurrounding sidechains are redesigned (mutated) to accommodate andstabilize the inserted epitope. Finally, as with superpositionepitope-scaffolds, mutations are made on the surface of the scaffold andoutside the epitope, to prevent clash or other interactions with theantibody. Grafting scaffolds require that the replaced segment andinserted epitope have similar translation and rotation transformationsbetween their N- and C-termini, and that the surrounding peptidebackbone does not clash with the inserted epitope. One differencebetween grafting and superposition is that grafting attempts to mimicthe epitope conformation exactly, whereas superposition allows for smallstructural deviations.

“De novo” epitope-scaffolds are computationally designed from scratch tooptimally present the crystallized conformation of the epitope. Thismethod is based on computational design of a novel fold (Kuhlman, B. etal. 2003 Science 302:1364-1368). The de novo allows design of immunogensthat are both minimal in size, so they do not present unwanted epitopes,and also highly stable against thermal or chemical denaturation.

The scaffold can be a heterologous scaffold. In several embodiments, thenative scaffold protein (without epitope insertion) is not a viralenvelope protein. In additional embodiments, the scaffold protein is nota RSV protein. In still further embodiments, the scaffold protein is nota viral protein.

In additional embodiments, the epitope-scaffold protein includes theamino acid sequence set forth as any one of SEQ ID NOs: 341-343, or apolypeptide with at least 80% sequence identity (such as at least 85%,at least 90%, at least 95%, at least 96%, at least 97%, at least 98% orat least 99% sequence identity) to any one of SEQ ID NOs: 341-343, andwherein the epitope-scaffold protein is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ). In additional embodiments, the RSV F protein is any one of SEQ IDNOs: 341-343, wherein the amino acid sequence of the RSV F protein hasup to 20 amino acid substitutions, and wherein the epitope scaffoldprotein is specifically bound by a prefusion-specific antibody (e.g.,D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø), in the absence of binding bythe corresponding prefusion-specific antibody (e.g., D25 or AM22antibody). Alternatively, the polypeptide can have none, or up to 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or 19 amino acidsubstitutions.

The recombinant RSV F protein stabilized in a prefusion conformation canbe placed anywhere in the scaffold, as long as the resultingepitope-scaffold protein is specifically bound by a prefusion-specificantibody (e.g., D25 or AM22 antibody), and/or includes a RSV F prefusionspecific conformation (such as antigenic site Ø), in the absence ofbinding by the corresponding prefusion-specific antibody (e.g., D25 orAM22 antibody). Methods for determining if a particular epitope-scaffoldprotein is specifically bound by a prefusion-specific antibody (e.g.,D25 or AM22 antibody) are disclosed herein and known to the person ofordinary skill in the art (see, for example, International ApplicationPub. Nos. WO 2006/091455 and WO 2005/111621). In addition, the formationof an antibody-antigen complex can be assayed using a number ofwell-defined diagnostic assays including conventional immunoassayformats to detect and/or quantitate antigen-specific antibodies. Suchassays include, for example, enzyme immunoassays, e.g., ELISA,cell-based assays, flow cytometry, radioimmunoassays, andimmunohistochemical staining. Numerous competitive and non-competitiveprotein binding assays are known in the art and many are commerciallyavailable. Methods for determining if a particular epitope-scaffoldprotein includes a RSV F prefusion specific conformation (such asantigenic site Ø), in the absence of binding by the correspondingprefusion-specific antibody (e.g., D25 or AM22 antibody) are alsodescribed herein and further known to the person of ordinary skill inthe art.

3. Virus-Like Particles

In some embodiments, a virus-like particle (VLP) is provided thatincludes a disclosed recombinant RSV F protein stabilized in a prefusionconformation. VLPs lack the viral components that are required for virusreplication and thus represent a highly attenuated form of a virus. TheVLP can display a polypeptide (e.g., a recombinant RSV F proteinstabilized in a prefusion conformation) that is capable of eliciting animmune response to RSV when administered to a subject. Virus likeparticles and methods of their production are known and familiar to theperson of ordinary skill in the art, and viral proteins from severalviruses are known to form VLPs, including human papillomavirus, HIV(Kang et al., Biol. Chem. 380: 353-64 (1999)), Semliki-Forest virus(Notka et al., Biol. Chem. 380: 341-52 (1999)), human polyomavirus(Goldmann et al., J. Virol. 73: 4465-9 (1999)), rotavirus (Jiang et al.,Vaccine 17: 1005-13 (1999)), parvovirus (Casal, Biotechnology andApplied Biochemistry, Vol 29, Part 2, pp 141-150 (1999)), canineparvovirus (Hurtado et al., J. Virol. 70: 5422-9 (1996)), hepatitis Evirus (Li et al., J. Virol. 71: 7207-13 (1997)), and Newcastle diseasevirus. For example, a chimeric VLP containing a RSV antigen and can be aNewcastle disease virus-based VLP. Newcastle disease based VLPs havepreviously been shown to elicit a neutralizing immune response to RSV inmice. The formation of such VLPs can be detected by any suitabletechnique. Examples of suitable techniques known in the art fordetection of VLPs in a medium include, e.g., electron microscopytechniques, dynamic light scattering (DLS), selective chromatographicseparation (e.g., ion exchange, hydrophobic interaction, and/or sizeexclusion chromatographic separation of the VLPs) and density gradientcentrifugation.

In some embodiments, the virus like particle includes a recombinant RSVF protein including an F2 polypeptide and a F1 polypeptide (such as anF1 polypeptide linked to a transmembrane domain), wherein the F1polypeptide includes a disulfide bond between a pair of cysteines atpositions 155 and 290, and a cavity-filling amino acid substitution atposition 190; or a disulfide bond between a pair of cysteines atpositions 155 and 290, a cavity-filling amino acid substitution atposition 190, and a cavity-filling amino acid substitution at position207.

In some embodiments, the virus like particle includes a recombinant RSVF protein including an F2 polypeptide and a F1 polypeptide (such as anF1 polypeptide linked to a transmembrane domain), wherein the F1polypeptide includes S155C, S290C, and S190F amino acid substitutions,S155C, S290C, and S190W amino acid substitutions, or S155C, S290C, andS190L amino acid substitutions. In further embodiments, the virus likeparticle includes a recombinant RSV F protein including an F2polypeptide and a F1 polypeptide (such as an F1 polypeptide linked to atransmembrane domain), wherein the F1 polypeptide includes S155C, S290C,S190F, and V207L amino acid substitutions, S155C, S290C, S190W, andV207L amino acid substitutions, S155C, S290C, S190L, and V207L aminoacid substitutions, S155C, S290C, S190F, and V207F amino acidsubstitutions, S155C, S290C, S190W, and V207F amino acid substitutions,S155C, S290C, S190L, and V207F amino acid substitutions, S155C, S290C,S190F, and V207W amino acid substitutions, S155C, S290C, S190W, andV207W amino acid substitutions, or S155C, S290C, S190L, and V207W aminoacid substitutions.

In some embodiments, the virus like particle includes a recombinant RSVF protein including an F2 polypeptide and a F1 polypeptide (such as anF1 polypeptide linked to a transmembrane domain), wherein the F₂polypeptide and the F₁ polypeptide include the amino acid sequence setforth as positions 26-109 and 137-513, respectively, of any one of SEQID NO: 371 (RSV A with S155C, S290C, S190F and V207L substitutions), SEQID NO: 372 (RSV B with S155C, S290C, S190F and V207L substitutions), SEQID NO: 373 (bovine RSV with S155C, S290C, S190F and V207Lsubstitutions), SEQ ID NO: 374 (RSV A with S155C, S290C, and S190Fsubstitutions), SEQ ID NO: 375 (RSV B with S155C, S290C, and S190Fsubstitutions); or SEQ ID NO: 376 (bovine RSV with S155C, S290C, andS190F substitutions).

In several embodiments, the virus like particle includes a recombinantRSV F protein including a F₁ polypeptide (such as an F1 polypeptidelinked to a transmembrane domain) and a F₂ polypeptide from a human RSVA subtype, a human RSV B subtype, or a bovine RSV, wherein the F1polypeptide includes any of the stabilizing modifications describedherein (e.g., one of the above combinations of stabilizing substitutionssuch as S155C, S290C, and S190F substitutions, or S155C, S290C, S190F,and V207L substitutions).

4. Protein Nanoparticles

In some embodiments a protein nanoparticle is provided that includes oneor more of any of the disclosed recombinant RSV F protein stabilized ina prefusion conformation, wherein the protein nanoparticle isspecifically bound by a prefusion-specific antibody (e.g., D25 or AM22antibody), and/or includes a RSV F prefusion specific conformation (suchas antigenic site Ø). Non-limiting example of nanoparticles includeferritin nanoparticles, an encapsulin nanoparticles and Sulfur OxygenaseReductase (SOR) nanoparticles, which are comprised of an assembly ofmonomeric subunits including ferritin proteins, encapsulin proteins andSOR proteins, respectively. To construct protein nanoparticles includingthe disclosed recombinant RSV F protein stabilized in a prefusionconformation, the antigen is linked to a subunit of the proteinnanoparticle (such as a ferritin protein, an encapsulin protein or a SORprotein). The fusion protein self-assembles into a nanoparticle underappropriate conditions.

Ferritin nanoparticles and their use for immunization purposes (e.g.,for immunization against influenza antigens) has been disclosed in theart (see, e.g., Kanekiyo et al., Nature, 499:102-106, 2013, incorporatedby reference herein in its entirety).

In some embodiments, any of the disclosed recombinant RSV F proteinsstabilized in a prefusion conformation are linked to a ferritinpolypeptide or hybrid of different ferritin polypeptides to construct aferritin protein nanoparticle, wherein the ferritin nanoparticle isspecifically bound by a prefusion-specific antibody (e.g., D25 or AM22antibody), and/or includes a RSV F prefusion specific conformation (suchas antigenic site Ø). Ferritin is a globular protein that is found inall animals, bacteria, and plants, and which acts primarily to controlthe rate and location of polynuclear Fe(III)₂O₃ formation through thetransportation of hydrated iron ions and protons to and from amineralized core. The globular form of ferritin is made up of monomericsubunits, which are polypeptides having a molecule weight ofapproximately 17-20 kDa. An example of the sequence of one suchmonomeric subunit is represented by SEQ ID NO: 353. Each monomericsubunit has the topology of a helix bundle which includes a fourantiparallel helix motif, with a fifth shorter helix (the c-terminalhelix) lying roughly perpendicular to the long axis of the 4 helixbundle. According to convention, the helices are labeled ‘A, B, C, D &E’ from the N-terminus respectively. The N-terminal sequence liesadjacent to the capsid three-fold axis and extends to the surface, whilethe E helices pack together at the four-fold axis with the C-terminusextending into the capsid core. The consequence of this packing createstwo pores on the capsid surface. It is expected that one or both ofthese pores represent the point by which the hydrated iron diffuses intoand out of the capsid. Following production, these monomeric subunitproteins self-assemble into the globular ferritin protein. Thus, theglobular form of ferritin comprises 24 monomeric, subunit proteins, andhas a capsid-like structure having 432 symmetry. Methods of constructingferritin nanoparticles are known to the person of ordinary skill in theart and are further described herein (see, e.g., Zhang, Int. J. Mol.Sci., 12:5406-5421, 2011, which is incorporated herein by reference inits entirety).

In specific examples, the ferritin polypeptide is E. coli ferritin,Helicobacter pylori ferritin, human light chain ferritin, bullfrogferritin or a hybrid thereof, such as E. coli-human hybrid ferritin, E.coli-bullfrog hybrid ferritin, or human-bullfrog hybrid ferritin.Exemplary amino acid sequences of ferritin polypeptides and nucleic acidsequences encoding ferritin polypeptides for use in the disclosed RSV Fprotein antigens stabilized in a prefusion conformation can be found inGENBANK®, for example at accession numbers ZP_03085328, ZP_06990637,EJB64322.1, AAA35832, NP_000137 AAA49532, AAA49525, AAA49524 andAAA49523, which are specifically incorporated by reference herein intheir entirety as available Feb. 28, 2013. In one embodiment, any of thedisclosed recombinant RSV F proteins stabilized in a prefusionconformation is linked to a ferritin protein including an amino acidsequence at least 80% (such as at least 85%, at least 90%, at least 95%,or at least 97%) identical to amino acid sequence set forth as SEQ IDNO: 353. A specific example of the disclosed recombinant RSV F proteinsstabilized in a prefusion conformation linked to a ferritin proteininclude the amino acid sequence set forth as SEQ ID NO: 350.

In some embodiments, the ferritin polypeptide is a Helicobacter pyloriferritin (such as a ferritin polypeptide set forth as SEQ ID NO: 353)and includes a substitution of the cysteine residue at position 31, suchas a C31S, C31A or C31V substitution. Any of the disclosed recombinantRSV F proteins (e.g., a RSV F polypeptide with S155C, S290C, and S190Fsubstitutions, or with S155C, S290C, S190F and V207L substitutions) canbe linked to a Helicobacter pylori ferritin (such as a ferritinpolypeptide set forth as SEQ ID NO: 353) that further includes asubstitution of the cysteine residue at position 31 of the ferritinpolypeptide, such as a C31S, C31A or C31V substitution.

In some embodiments, the ferritin protein nanoparticle includes arecombinant RSV F protein including an F2 polypeptide and a F1polypeptide, wherein the F1 polypeptide is linked to the ferritinprotein, and wherein the F1 polypeptide includes a disulfide bondbetween a pair of cysteines at positions 155 and 290, and acavity-filling amino acid substitution at position 190; or a disulfidebond between a pair of cysteines at positions 155 and 290, acavity-filling amino acid substitution at position 190, and acavity-filling amino acid substitution at position 207.

In some embodiments, the ferritin protein nanoparticle includes arecombinant RSV F protein including an F2 polypeptide and a F1polypeptide, wherein the F1 polypeptide is linked to the ferritinprotein, and wherein the F1 polypeptide includes S155C, S290C, and S190Famino acid substitutions, S155C, S290C, and S190W amino acidsubstitutions, or S155C, S290C, and S190L amino acid substitutions. Infurther embodiments, the ferritin protein nanoparticle includes arecombinant RSV F protein including an F2 polypeptide and a F1polypeptide, wherein the F1 polypeptide is linked to the ferritinprotein, and wherein the F1 polypeptide includes S155C, S290C, S190F,and V207L amino acid substitutions, S155C, S290C, S190W, and V207L aminoacid substitutions, S155C, S290C, S190L, and V207L amino acidsubstitutions, S155C, S290C, S190F, and V207F amino acid substitutions,S155C, S290C, S190W, and V207F amino acid substitutions, S155C, S290C,S190L, and V207F amino acid substitutions, S155C, S290C, S190F, andV207W amino acid substitutions, S155C, S290C, S190W, and V207W aminoacid substitutions, or S155C, S290C, S190L, and V207W amino acidsubstitutions.

The RSV F protein included on the ferritin nanoparticle can be a humansubtype A, human subtype B or bovine RSV F protein include thesubstitutions disclosed herein for prefusion stabilization.

In some embodiments, the ferritin protein nanoparticle includes arecombinant RSV F protein including an F2 polypeptide and a F1polypeptide, wherein the F1 polypeptide is linked to the ferritinprotein, and wherein the F₂ polypeptide and the F₁ polypeptide includethe amino acid sequence set forth as positions 26-109 and 137-513,respectively, of any one of SEQ ID NO: 371 (RSV A with S155C, S290C,S190F and V207L substitutions), SEQ ID NO: 372 (RSV B with S155C, S290C,S190F and V207L substitutions), SEQ ID NO: 373 (bovine RSV with S155C,S290C, S190F and V207L substitutions), SEQ ID NO: 374 (RSV A with S155C,S290C, and S190F substitutions), SEQ ID NO: 375 (RSV B with S155C,S290C, and S190F substitutions); or SEQ ID NO: 376 (bovine RSV withS155C, S290C, and S190F substitutions). In one non-limiting embodiment,the. In several embodiments, the ferritin protein nanoparticle includesa recombinant RSV F protein including a F₁ polypeptide and a F₂polypeptide from a human RSV A subtype, a human RSV B subtype, or abovine RSV, wherein the F1 polypeptide includes any of the stabilizingmodifications described herein (e.g., one of the above combinations ofstabilizing substitutions such as S155C, S290C, and S190F substitutions,or S155C, S290C, S190F, and V207L substitutions).

In some embodiments the ferritin nanoparticle includes a recombinant RSVF protein including an F2 polypeptide and a F1 polypeptide, wherein theF1 polypeptide is linked to the ferritin protein, and wherein the F₂polypeptide and the F₁ polypeptide linked to the ferritin proteininclude the amino acid sequence set forth as positions 26-109 and137-679, respectively of SEQ ID NO: 377 (RSV A including S155C, S290C,S190F, V207L amino acid substitutions, with C-terminal ferritin domain),or SEQ ID NOs: 378-382.

In some embodiments the ferritin nanoparticle includes a recombinant RSVF protein including an F2 polypeptide and a F1 polypeptide, wherein theF1 polypeptide is linked to ferritin, and wherein the F₂ polypeptide andthe F₁ polypeptide linked to ferritin include the amino acidsubstitutions listed in row 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, or49 of column 3 of Table 8e. In some embodiments the ferritinnanoparticle includes a recombinant RSV F protein including an F2polypeptide and a F1 polypeptide, wherein the F1 polypeptide is linkedto the ferritin protein, and wherein the F₂ polypeptide and the F₁polypeptide linked to the ferritin protein include the amino acidsequence of the F1 and F2 polypeptide set forth in the SEQ ID NO listedin row 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, or 49 of column 4 ofTable 8e. It will be appreciated that SEQ ID NOs. 602-617 and 620-634and 645-650 listed in Table 8e include signal sequence and pep27polypeptide sequences, which are removed by proteolytic processing whenthe corresponding F protein is made in eukaryotic cells, as well asC-terminal protein tags.

TABLE 8e Exemplary RSV F protein mutations and sequences for productionof ferritin nanoparticles Row Description Substitutions/modificationsSEQ ID NO 1 Cavity filling (S155C, S290C, S190F, V207L) + L230F 602 2Cavity filling (S155C, S290C, S190F, V207L) + L158F 603 3 Cavity filling(S155C, S290C, S190F, V207L) + 604 L230F/L158F 4 DSCav1 + replaceexposed (S155C, S290C, S190F, V207L) + 605 hydrophobic residuesL160K/V178T/L258K/V384T/I431S/L467Q/ 5 DSCav1 + replace exposed (S155C,S290C, S190F, V207L) + 606 hydrophobic residuesF477K/L481Q/V482K/L503Q/I506K 6 DSCav1 + replace exposed (S155C, S290C,S190F, V207L) + 607 hydrophobic residuesL160K/V178T/L258K/V384T/I431S/L467Q/ F477K/L481Q/V482K/L503Q/I506K 7Cavity filling + replace (S155C, S290C, S190F, V207L) + 608 exposedhydrophobic L158F/L230F/L83F/V90F/I506K/I395F/V185F/ residues T54A 8Cavity filling + replace (S155C, S290C, S190F, V207L) + 609 exposedhydrophobic L83F/V90F/I506K residues 9 DS-S190F with C-terminal S190F,S155C, S290C, F488W, L513C, 610 Cys ring1 A514E, I515C 10 DS-S190F withC-terminal S190F, S155C, S290C, F488W, L513C, 611 Cys ring2 A514E,G515E, 516C 11 DS-S190F with C-terminal S190F, S155C, S290C, F488W,L512C, 612 Cys ring3 L513E, A514C 12 DS-S190F with C-terminal S190F,S155C, S290C, F488W, L512C, 613 Cys ring4 L513E, A514E, G515C 13DS-S190F with Foldon S190F, S155C, S290C, F488W, Foldon 614 14 DS-S190Fwith 1 extra S190F, S155C, S290C, L171C, K191C, 615 disulfide bridgewith F488W, Foldon Foldon 15 DS-S190F with 2 extra S190F, S155C, S290C,A424C, V450C, 616 disulfide bridges with L171C, K191C, F488W, FoldonFoldon 16 DS-S190F with 3 extra K77C, I217C, S190F, S155C, S290C, 617disulfide bridges with A424C, V450C, L171C, K191C, F488W, Foldon Foldon17 Single chain and shorten F Single chain F with (S155C, S290C, 618protein to end at residue S190F, V207L) 513 18 Single chain and shortenF Single chain F with(S155C, S290C, 619 protein to end at residue S190F,V207L) 492 19 Disulfide ferritin: S29C/C31S/V68C 620 20 Disulfideferritin: C31S/A115C/H128C 621 21 Disulfide + cavity fillingL158F/L203F/V2961; Ferritin: 622 S29C/C31S/V68C/A115C/H128C 22Disulfide + cavity filling Y198F/T219L/K226M; ferritin: 623C31S/A115C/H128C 23 Disulfide + cavity filling E82V/K226M/N227L/V296I;ferritin: 624 C31S/A115C/H128C 24 Improved purification of (S155C,S290C, S190F, V207L) + and 625 DSCav1 Ferritin particles DYKDDDDKGG(Res. 26-35 of SEQ ID NO: 625 insertion at N-terminus of F 25 Improvedpurification of (S155C, S290C, S190F, V207L) + and 626 DSCav1 Ferritinparticles QHHHHHHGG (Res. 26-34 of SEQ ID NO: 626 insertion atN-terminus F 26 Improved purification of (S155C, S290C, S190F, V207L) +and 627 DSCav1 Ferritin particles QHHHHHHHHGG (Res. 26-36 of SEQ ID NO:627 insertion at N-terminus F 27 Improved purification of (S155C, S290C,S190F, V207L) + and 628 DSCav1 Ferritin particles GGHHHHHHGG (Res.328-337 of SEQ ID NO: 628 insertion at residue 327 of F 28 Improvedpurification of (S155C, S290C, S190F, V207L) + and 629 DSCav1 Ferritinparticles GGHHHHHHHHGG (Res. 328-339 of SEQ ID NO: 629 insertion atresidue 327 of F 29 Improved purification of (S155C, S290C, S190F,V207L) + and 630 DSCavl Ferritin particles HHHHH (Res. 324-338 of SEQ IDNO: 630 insertion at residue 323 of F 30 Improved purification of(S155C, S290C, S190F, V207L) + and 631 DSCav1 Ferritin particlesQSAWSHPQFEKHHHHHHGGLVPRGSGG (Res. 26-52 of SEQ ID NO: 631 insertion atN- terminus of F 31 Improved purification of (S155C, S290C, S190F,V207L) + and 632 DSCav1 Ferritin particles QSAWSHPQFEKHHHHHHGGLVPRGSGG(Res. 26-52 of SEQ ID NO: 631 insertion at N- terminus of F 32 Longerlinker between RSV (S155C, S290C, S190F, V207L) + 10 aa 633 F DSCav1 andFerritin linker to Ferritin 33 Longer linker between RSV (S155C, S290C,S190F, V207L) + N500Q + 634 F DSCav1 and Ferritin 10 aa linker toFerritin 34 single chain end at DS-Cav1 single chain with longer linker635 residue 513, longer linker 35 single chain end at DS-Cav1 singlechain with longer linker 636 residue 492 longer linker 36 single chainend at DS-Cav1 single chain with N500Q 637 residue 513, N500Q removeglycan 37 single chain end at DS-Cav1 single chain with longer linker638 residue 513, longer linker N500Q N500Q remove glycan 38 single chainRSV F DS-Cav1 S155C, S290C, S190F, V207L single chain 639 and FerritinN105-G145 linkGS 39 single chain RSV F DS-Cav1 S155C, S290C, S190F,V207L, N500Q 640 and Ferritin end at 492 single chain end at 492N105-G145 linkGS 40 single chain RSV F DS-Cav1 S155C, S290C, S190F,V207L single chain 641 and Ferritin longer linker N105-G145 + 10 aalinker to Ferritin 41 single chain RSV F DS-Cav1 S155C, S290C, S190F,V207L, N500Q 642 and Ferritin end at 492 single chain end at 492N105-G145 + longer linker 10 aa linker to Ferritin 42 single chain RSV FDS-Cav1 S155C, S290C, S190F, V207L, N500Q 643 and Ferritin and removesingle chain N105-G145 linkGS N500 glycan 43 single chain RSV F DS-Cav1S155C, S290C, S190F, V207L, N500Q 644 and Ferritin longer linker singlechain N105-G145 + 10 aa linker and remove N500 glycan to Ferritin 44DS-cav1 + exposed DS-cav1 + 645 hydrophobic + 10 aa linkerL160K/V178T/L258K/V384T/I431S/L467Q/ + 10 aa linker 45 DS-cav1 + exposedDS-cav1 + F477K/L481Q/V482K/L503Q/I506K + 646 hydrophobic + 10 aa linker10 aa linker 46 DS-cav1 + exposed DS-cav1 + 647 hydrophobic + 10 aalinker L160K/V178T/L258K/V384T/I431S/L467Q/F477K/L481Q/V482K/L503Q/I506K + 10 aa linker 47 DS-cav1 + exposedDS-cav1 + 648 hydrophobic + 10 aa linker +L160K/V178T/L258K/V384T/I431S/L467Q/ + N500 glycan removal 10 aalinker + N500Q 48 DS-cav1 + exposed DS-cav1 +F477K/L481Q/V482K/L503Q/I506K + 649 hydrophobic + 10 aa linker + 10 aalinker + N500Q N500 glycan removal 49 DS-cav1 + exposed DS-cav1 + 650hydrophobic + 10 aa linker + L160K/V178T/L258K/V384T/I431S/L467Q/ N500glycan removal F477K/L481Q/V482K/L503Q/I506K + 10 aa linker + N500Q

In additional embodiments, any of the disclosed RSV F protein antigensstabilized in a prefusion conformation are linked to an encapsulinpolypeptide to construct an encapsulin nanoparticle, wherein theencapsulin nanoparticle is specifically bound by a prefusion-specificantibody (e.g., D25 or AM22 antibody), and/or includes a RSV F prefusionspecific conformation (such as antigenic site Ø). Encapsulin proteinsare a conserved family of bacterial proteins also known as linocin-likeproteins that form large protein assemblies that function as a minimalcompartment to package enzymes. The encapsulin assembly is made up ofmonomeric subunits, which are polypeptides having a molecule weight ofapproximately 30 kDa. An example of the sequence of one such monomericsubunit is provided as SEQ ID NO: 354. Following production, themonomeric subunits self-assemble into the globular encapsulin assemblyincluding 60 monomeric subunits. Methods of constructing encapsulinnanoparticles are known to the person of ordinary skill in the art, andfurther described herein (see, for example, Sutter et al., NatureStruct. and Mol. Biol., 15:939-947, 2008, which is incorporated byreference herein in its entirety). In specific examples, the encapsulinpolypeptide is bacterial encapsulin, such as E. coli or Thermotogamaritime encapsulin. An exemplary encapsulin sequence for use with thedisclosed RSV F protein antigens stabilized in a prefusion conformationis set forth as SEQ ID NO: 354.

In additional embodiments, any of the disclosed recombinant RSV Fproteins stabilized in a prefusion conformation are linked to a SulferOxygenase Reductase (SOR) polypeptide to construct a SOR nanoparticle,wherein the SOR nanoparticle is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ). SOR proteins are microbial proteins (for example from thethermoacidophilic archaeon Acidianus ambivalens that form 24 subunitprotein assemblies. Methods of constructing SOR nanoparticles are knownto the person of ordinary skill in the art (see, e.g., Urich et al.,Science, 311:996-1000, 2006, which is incorporated by reference hereinin its entirety). Specific examples of the disclosed recombinant RSV Fproteins stabilized in a prefusion conformation linked to a SOR proteininclude the amino acid sequences set forth as SEQ ID NO: 344 and SEQ IDNO: 345.

In additional embodiments, any of the disclosed recombinant RSV Fproteins stabilized in a prefusion conformation are linked to a Lumazinesynthase polypeptide to construct a Lumazine synthase nanoparticle,wherein the Lumazine synthase nanoparticle is specifically bound by aprefusion-specific antibody (e.g., D25 or AM22 antibody), and/orincludes a RSV F prefusion specific conformation (such as antigenic siteØ). Specific examples of the disclosed recombinant RSV F proteinsstabilized in a prefusion conformation linked to a Lumazine synthaseprotein include the amino acid sequences set forth as SEQ ID NOs:346-348.

In additional embodiments, any of the disclosed recombinant RSV Fproteins stabilized in a prefusion conformation are linked to a pyruvatedehydrogenase polypeptide to construct a pyruvate dehydrogenasenanoparticle, wherein the pyruvate dehydrogenase nanoparticle isspecifically bound by a prefusion-specific antibody (e.g., D25 or AM22antibody), and/or includes a RSV F prefusion specific conformation (suchas antigenic site Ø). A specific example of the disclosed recombinantRSV F proteins stabilized in a prefusion conformation linked to apyruvate dehydrogenase protein include the amino acid sequence set forthas SEQ ID NO: 349.

In some examples, any of the disclosed recombinant RSV F proteinsstabilized in a prefusion conformation is linked to the N- or C-terminusof a ferritin, encapsulin, SOR, lumazine synthase or pyruvatedehydrogenase protein, for example with a linker, such as a Ser-Glylinker. When the constructs have been made in HEK 293 Freestyle cells,the fusion proteins are secreted from the cells and self-assembled intonanoparticles. The nanoparticles can be purified using known techniques,for example by a few different chromatography procedures, e.g. Mono Q(anion exchange) followed by size exclusion (SUPEROSE® 6)chromatography.

Several embodiments include a monomeric subunit of a ferritin,encapsulin, SOR, lumazine synthase or pyruvate dehydrogenase protein, orany portion thereof which is capable of directing self-assembly ofmonomeric subunits into the globular form of the protein. Amino acidsequences from monomeric subunits of any known ferritin, encapsulin,SOR, lumazine synthase or pyruvate dehydrogenase protein can be used toproduce fusion proteins with the disclosed recombinant RSV F proteinsstabilized in a prefusion conformation, so long as the monomeric subunitis capable of self-assembling into a nanoparticle displaying therecombinant RSV F proteins stabilized in a prefusion conformation on itssurface.

The fusion proteins need not comprise the full-length sequence of amonomeric subunit polypeptide of a ferritin, encapsulin, SOR, lumazinesynthase or pyruvate dehydrogenase protein. Portions, or regions, of themonomeric subunit polypeptide can be utilized so long as the portioncomprises amino acid sequences that direct self-assembly of monomericsubunits into the globular form of the protein.

In some embodiments, it may be useful to engineer mutations into theamino acid sequence of the monomeric ferritin, encapsulin, SOR, lumazinesynthase or pyruvate dehydrogenase subunits. For example, it may beuseful to alter sites such as enzyme recognition sites or glycosylationsites in order to give the fusion protein beneficial properties (e.g.,half-life).

It will be understood by those skilled in the art that fusion of any ofthe disclosed recombinant RSV F proteins stabilized in a prefusionconformation to the ferritin, encapsulin, SOR, lumazine synthase orpyruvate dehydrogenase protein should be done such that the disclosedrecombinant RSV F proteins stabilized in a prefusion conformationportion of the fusion protein does not interfere with self-assembly ofthe monomeric ferritin, encapsulin, SOR, lumazine synthase or pyruvatedehydrogenase subunits into the globular protein, and that the ferritin,encapsulin, SOR, lumazine synthase or pyruvate dehydrogenase proteinportion of the fusion protein does not interfere with the ability of thedisclosed recombinant RSV F protein antigen stabilized in a prefusionconformation to elicit an immune response to RSV. In some embodiments,the ferritin, encapsulin, SOR, lumazine synthase or pyruvatedehydrogenase protein and disclosed recombinant RSV F protein stabilizedin a prefusion conformation can be joined together directly withoutaffecting the activity of either portion. In other embodiments, theferritin, encapsulin, SOR, lumazine synthase or pyruvate dehydrogenaseprotein and the recombinant RSV F protein stabilized in a prefusionconformation are joined using a linker (also referred to as a spacer)sequence. The linker sequence is designed to position the ferritin,encapsulin, SOR, lumazine synthase or pyruvate dehydrogenase portion ofthe fusion protein and the disclosed recombinant RSV F proteinstabilized in a prefusion conformation portion of the fusion protein,with regard to one another, such that the fusion protein maintains theability to assemble into nanoparticles, and also elicit an immuneresponse to RSV. In several embodiments, the linker sequences compriseamino acids. Preferable amino acids to use are those having small sidechains and/or those which are not charged. Such amino acids are lesslikely to interfere with proper folding and activity of the fusionprotein. Accordingly, preferred amino acids to use in linker sequences,either alone or in combination are serine, glycine and alanine. Oneexample of such a linker sequence is SGG. Amino acids can be added orsubtracted as needed. Those skilled in the art are capable ofdetermining appropriate linker sequences for construction of proteinnanoparticles.

In certain embodiments, the protein nanoparticles have a molecularweight of from 100 to 5000 kDa, such as approximately 500 to 4600 kDa.In some embodiments, a Ferritin nanoparticle has an approximatemolecular weight of 650 kDa, an Encapsulin nanoparticle has anapproximate molecular weight of 2100 kDa, a SOR nanoparticle has anapproximate molecular weight of 1000 kDa, a lumazine synthasenanoparticle has an approximate molecular weight of 4000 kDa, and apyruvate dehydrogenase nanoparticle has an approximate molecular weightof 4600 kDa, when the protein nanoparticle include a recombinant RSV Fprotein stabilized in a prefusion conformation.

The disclosed recombinant RSV F proteins stabilized in a prefusionconformation linked to ferritin, encapsulin, SOR, lumazine synthase orpyruvate dehydrogenase proteins can self-assemble into multi-subunitprotein nanoparticles, termed ferritin nanoparticles, encapsulinnanoparticles, SOR nanoparticles, lumazine synthase nanoparticles, andpyruvate dehydrogenase nanoparticles, respectively. The nanoparticlesinclude the disclosed recombinant RSV F proteins stabilized in aprefusion conformation have substantially the same structuralcharacteristics as the native ferritin, encapsulin, SOR, lumazinesynthase or pyruvate dehydrogenase nanoparticles that do not include thedisclosed recombinant RSV F proteins stabilized in a prefusionconformation. That is, they contain 24, 60, 24, 60, or 60 subunits(respectively) and have similar corresponding symmetry. In the case ofnanoparticles constructed of monomer subunits including a disclosedrecombinant RSV F protein stabilized in a prefusion conformation, suchnanoparticles are specifically bound by a prefusion-specific antibody(e.g., D25 or AM22 antibody), and/or includes a RSV F prefusion specificconformation (such as antigenic site Ø).

C. Polynucleotides Encoding Antigens

Polynucleotides encoding the disclosed PreF antigens (e.g., arecombinant RSV F protein stabilized in a prefusion conformation, orepitope-scaffold protein, or virus-like particle or protein nanoparticlecontaining such proteins) are also provided. These polynucleotidesinclude DNA, cDNA and RNA sequences which encode the antigen.

In some embodiments, the nucleic acid molecule encodes a precursor F₀polypeptide that, when expressed in an appropriate cell, is processedinto a disclosed PreF antigen. In some embodiments, the nucleic acidmolecule encodes a precursor F₀ polypeptide that, when expressed in anappropriate cell, is processed into a disclosed PreF antigen, whereinthe precursor F₀ polypeptide includes, from N- to C-terminus, a signalpeptide, a F₂ polypeptide, a Pep27 polypeptide, and a F₁ polypeptide. Insome embodiments, the Pep27 polypeptide includes the amino acid sequenceset forth as positions 110-136 of any one SEQ ID NOs: 1-184 or 370,wherein the amino acid positions correspond to the amino acid sequenceof a reference F₀ polypeptide set forth as SEQ ID NO: 124. In someembodiments, the signal peptide includes the amino acid sequence setforth as positions 1-25 of any one SEQ ID NOs: 1-184 or 370, wherein theamino acid positions correspond to the amino acid sequence of areference F₀ polypeptide set forth as SEQ ID NO: 124.

In some embodiments, the nucleic acid molecule encodes a precursor F₀polypeptide that, when expressed in an appropriate cell, is processedinto a disclosed PreF antigen, wherein the precursor F₀ polypeptideincludes the amino acid sequence set forth as any one of SEQ ID NOs:185, or 189-303. In some embodiments, the nucleic acid molecule encodesa precursor F₀ polypeptide that, when expressed in an appropriate cell,is processed into a disclosed PreF antigen, wherein the precursor F₀polypeptide includes the amino acid sequence set forth as residues 1-513of any one of SEQ ID NOs: 185, or 189-303.

In some embodiments, the nucleic acid molecule encodes a precursor F₀polypeptide that, when expressed in an appropriate cell, is processedinto a disclosed PreF antigen including a recombinant RSV F proteinincluding an F2 polypeptide and a F1 polypeptide, and wherein the F1polypeptide includes a disulfide bond between a pair of cysteines atpositions 155 and 290, and a cavity-filling amino acid substitution atposition 190; or a disulfide bond between a pair of cysteines atpositions 155 and 290, a cavity-filling amino acid substitution atposition 190, and a cavity-filling amino acid substitution at position207.

In some embodiments, the nucleic acid molecule encodes a precursor F₀polypeptide that, when expressed in an appropriate cell, is processedinto a disclosed PreF antigen including a recombinant RSV F proteinincluding an F2 polypeptide and a F1 polypeptide, and wherein the F1polypeptide includes S155C, S290C, and S190F amino acid substitutions,S155C, S290C, and S190W amino acid substitutions, or S155C, S290C, andS190L amino acid substitutions. In further embodiments, the nucleic acidmolecule encodes a precursor F₀ polypeptide that, when expressed in anappropriate cell, is processed into a disclosed PreF antigen including arecombinant RSV F protein including an F2 polypeptide and a F1polypeptide, and wherein the F1 polypeptide includes S155C, S290C,S190F, and V207L amino acid substitutions, S155C, S290C, S190W, andV207L amino acid substitutions, S155C, S290C, S190L, and V207L aminoacid substitutions, S155C, S290C, S190F, and V207F amino acidsubstitutions, S155C, S290C, S190W, and V207F amino acid substitutions,S155C, S290C, S190L, and V207F amino acid substitutions, S155C, S290C,S190F, and V207W amino acid substitutions, S155C, S290C, S190W, andV207W amino acid substitutions, or S155C, S290C, S190L, and V207W aminoacid substitutions.

In some embodiments, the nucleic acid molecule encodes a precursor F₀polypeptide that, when expressed in an appropriate cell, is processedinto a disclosed PreF antigen including a recombinant RSV F proteinincluding an F2 polypeptide and a F1 polypeptide, wherein the F₂polypeptide and the F₁ polypeptide include the amino acid sequence setforth as positions 26-109 and 137-513, respectively, of any one of SEQID NO: 371 (RSV A with S155C, S290C, S190F and V207L substitutions), SEQID NO: 372 (RSV B with S155C, S290C, S190F and V207L substitutions), SEQID NO: 373 (bovine RSV with S155C, S290C, S190F and V207Lsubstitutions), SEQ ID NO: 374 (RSV A with S155C, S290C, and S190Fsubstitutions), SEQ ID NO: 375 (RSV B with S155C, S290C, and S190Fsubstitutions); or SEQ ID NO: 376 (bovine RSV with S155C, S290C, andS190F substitutions).

In several embodiments, the nucleic acid molecule encodes a precursor F₀polypeptide that, when expressed in an appropriate cell, is processedinto a disclosed PreF antigen including a recombinant RSV F proteinincluding an F2 polypeptide and a F1 polypeptide from a human RSV Asubtype, a human RSV B subtype, or a bovine RSV, wherein the F1polypeptide includes any of the stabilizing modifications describedherein (e.g., one of the above combinations of stabilizing substitutionssuch as S155C, S290C, and S190F substitutions, or S155C, S290C, S190F,and V207L substitutions).

In one non-limiting example the nucleic acid molecule encodes aprecursor F₀ polypeptide that, when expressed in an appropriate cell, isprocessed into a disclosed PreF antigen including a recombinant RSV Fprotein including an F2 polypeptide and a F1 polypeptide, wherein the F1polypeptide is linked to a ferritin protein, and wherein the F₂polypeptide and the F₁ polypeptide linked to the ferritin proteininclude the amino acid sequence set forth as positions 26-109 and137-679, respectively of SEQ ID NO: 377 (RSV A including S155C, S290C,S190F, V207L amino acid substitutions, with C-terminal ferritin domain),or SEQ ID NOs: 378-382.

In one non-limiting example, the nucleic acid molecule includes thesequence set forth as SEQ ID NO: 383 (RSV F protein from human subtype Aincluding S155C, S290C, S190F and V207L amino acid substitutions, fusedto a C-terminal Foldon domain, thrombin cleavage site, 6×His tag and aStrepTag II).

In another non-limiting example, the nucleic acid molecule is anexpression vector, and includes the sequence set forth as SEQ ID NO: 384(RSV F protein from human subtype A including S155C, S290C, S190F andV207L amino acid substitutions, fused to a C-terminal Foldon domain,thrombin cleavage site, 6×His tag and a StrepTag II).

Methods for the manipulation and insertion of the nucleic acids of thisdisclosure into vectors are well known in the art (see for example,Sambrook et al., Molecular Cloning, a Laboratory Manual, 2d edition,Cold Spring Harbor Press, Cold Spring Harbor, N.Y., 1989, and Ausubel etal., Current Protocols in Molecular Biology, Greene PublishingAssociates and John Wiley & Sons, New York, N.Y., 1994).

A nucleic acid encoding PreF antigens (e.g., a recombinant RSV F proteinstabilized in a prefusion conformation, or epitope-scaffold protein, orvirus-like particle or protein nanoparticle containing such proteins)can be cloned or amplified by in vitro methods, such as the polymerasechain reaction (PCR), the ligase chain reaction (LCR), thetranscription-based amplification system (TAS), the self-sustainedsequence replication system (3SR) and the Qβ replicase amplificationsystem (QB). For example, a polynucleotide encoding the protein can beisolated by polymerase chain reaction of cDNA using primers based on theDNA sequence of the molecule. A wide variety of cloning and in vitroamplification methodologies are well known to persons skilled in theart. PCR methods are described in, for example, U.S. Pat. No. 4,683,195;Mullis et al., Cold Spring Harbor Symp. Quant. Biol. 51:263, 1987; andErlich, ed., PCR Technology, (Stockton Press, N Y, 1989).Polynucleotides also can be isolated by screening genomic or cDNAlibraries with probes selected from the sequences of the desiredpolynucleotide under stringent hybridization conditions.

The polynucleotides encoding PreF antigens (e.g., a recombinant RSV Fprotein stabilized in a prefusion conformation, or epitope-scaffoldprotein, or virus-like particle or protein nanoparticle containing suchproteins) include a recombinant DNA which is incorporated into a vectorinto an autonomously replicating plasmid or virus or into the genomicDNA of a prokaryote or eukaryote, or which exists as a separate molecule(such as a cDNA) independent of other sequences. The nucleotides can beribonucleotides, deoxyribonucleotides, or modified forms of eithernucleotide. The term includes single and double forms of DNA.

DNA sequences encoding PreF antigens (e.g., a recombinant RSV F proteinstabilized in a prefusion conformation, or epitope-scaffold protein, orvirus-like particle or protein nanoparticle containing such proteins)can be expressed in vitro by DNA transfer into a suitable host cell. Thecell may be prokaryotic or eukaryotic. The term also includes anyprogeny of the subject host cell. It is understood that all progeny maynot be identical to the parental cell since there may be mutations thatoccur during replication. Methods of stable transfer, meaning that theforeign DNA is continuously maintained in the host, are known in theart.

Polynucleotide sequences encoding PreF antigens (e.g., a recombinant RSVF protein stabilized in a prefusion conformation, or epitope-scaffoldprotein, or virus-like particle or protein nanoparticle containing suchproteins) can be operatively linked to expression control sequences. Anexpression control sequence operatively linked to a coding sequence isligated such that expression of the coding sequence is achieved underconditions compatible with the expression control sequences. Theexpression control sequences include, but are not limited to,appropriate promoters, enhancers, transcription terminators, a startcodon (i.e., ATG) in front of a protein-encoding gene, splicing signalfor introns, maintenance of the correct reading frame of that gene topermit proper translation of mRNA, and stop codons.

Hosts can include microbial, yeast, insect and mammalian organisms.Methods of expressing DNA sequences having eukaryotic or viral sequencesin prokaryotes are well known in the art. Non-limiting examples ofsuitable host cells include bacteria, archea, insect, fungi (forexample, yeast), plant, and animal cells (for example, mammalian cells,such as human). Exemplary cells of use include Escherichia coli,Bacillus subtilis, Saccharomyces cerevisiae, Salmonella typhimurium, SF9cells, C129 cells, 293 cells, Neurospora, and immortalized mammalianmyeloid and lymphoid cell lines. Techniques for the propagation ofmammalian cells in culture are well-known (see, Jakoby and Pastan (eds),1979, Cell Culture. Methods in Enzymology, volume 58, Academic Press,Inc., Harcourt Brace Jovanovich, N.Y.). Examples of commonly usedmammalian host cell lines are VERO and HeLa cells, CHO cells, and WI38,BHK, and COS cell lines, although cell lines may be used, such as cellsdesigned to provide higher expression, desirable glycosylation patterns,or other features. In some embodiments, the host cells include HEK293cells or derivatives thereof, such as GnTI^(−/−) cells (ATCC® No.CRL-3022).

Transformation of a host cell with recombinant DNA can be carried out byconventional techniques as are well known to those skilled in the art.Where the host is prokaryotic, such as, but not limited to, E. coli,competent cells which are capable of DNA uptake can be prepared fromcells harvested after exponential growth phase and subsequently treatedby the CaCl₂ method using procedures well known in the art.Alternatively, MgCl₂ or RbCl can be used. Transformation can also beperformed after forming a protoplast of the host cell if desired, or byelectroporation.

When the host is a eukaryote, such methods of transfection of DNA ascalcium phosphate coprecipitates, conventional mechanical proceduressuch as microinjection, electroporation, insertion of a plasmid encasedin liposomes, or viral vectors can be used. Eukaryotic cells can also beco-transformed with polynucleotide sequences encoding a disclosedantigen, and a second foreign DNA molecule encoding a selectablephenotype, such as the herpes simplex thymidine kinase gene. Anothermethod is to use a eukaryotic viral vector, such as simian virus 40(SV40) or bovine papilloma virus, to transiently infect or transformeukaryotic cells and express the protein (see for example, EukaryoticViral Vectors, Cold Spring Harbor Laboratory, Gluzman ed., 1982).

D. Viral Vectors

The nucleic acid molecules encoding a recombinant RSV F proteinstabilized in a prefusion conformation can be included in a viralvector, for example for expression of the antigen in a host cell, or forimmunization of a subject as disclosed herein. In some embodiments, theviral vectors are administered to a subject as part of a prime-boostvaccination. In several embodiments, the viral vectors are included in avaccine, such as a primer vaccine or a booster vaccine for use in aprime-boost vaccination.

In several examples, the viral vector encoding the recombinant RSV Fprotein stabilized in a prefusion conformation can bereplication-competent. For example, the viral vector can have a mutation(e.g., insertion of nucleic acid encoding the PreF antigen) in the viralgenome that does not inhibit viral replication in host cells. The viralvector also can be conditionally replication-competent. In otherexamples, the viral vector is replication-deficient in host cells.

In several embodiments, the recombinant RSV F protein stabilized in aprefusion conformation is expressed by a viral vector that can bedelivered via the respiratory tract. For example, a paramyxovirus (PIV)vector, such as bovine parainfluenza virus (BPIV) vector (e.g., aBPIV-1, BPIV-2, or BPV-3 vector) or human PIV vector, a metapneumovirus(MPV) vector, a Sendia virus vector, or a measles virus vector, is usedto express a disclosed antigen. A BPIV3 viral vector expressing the RSVF and the hPIV F proteins (MEDI-534) is currently in clinical trials asa RSV vaccine. Examples of paramyxovirus (PIV) vector for expressingantigens are known to the person of skill in the art (see, e.g., U.S.Pat. App. Pubs. 2012/0045471, 2011/0212488, 2010/0297730, 2010/0278813,2010/0167270, 2010/0119547, 2009/0263883, 2009/0017517, 2009/0004722,2008/0096263, 2006/0216700, 2005/0147623, 2005/0142148, 2005/0019891,2004/0208895, 2004/0005545, 2003/0232061, 2003/0095987, and2003/0072773; each of which is incorporated by reference herein in itsentirety). In another example, a Newcastle disease viral vector is usedto express a disclosed antigen (see, e.g., McGinnes et al., J. Virol.,85: 366-377, 2011, describing RSV F and G proteins expressed onNewcastle disease like particles, incorporated by reference in itsentirety). In another example, a Sendai virus vector is used to expressa disclosed antigen (see, e.g., Jones et al., Vaccine, 30:959-968, 2012,incorporated by reference herein in its entirety, which discloses use ofa Sendai virus-based RSV vaccine to induce an immune response inprimates).

Additional viral vectors are also available for expression of thedisclosed antigens, including polyoma, i.e., SV40 (Madzak et al., 1992,J. Gen. Virol., 73:15331536), adenovirus (Berkner, 1992, Cur. Top.Microbiol. Immunol., 158:39-6; Berliner et al., 1988, Bio Techniques,6:616-629; Gorziglia et al., 1992, J. Virol., 66:4407-4412; Quantin etal., 1992, Proc. Natl. Acad. Sci. USA, 89:2581-2584; Rosenfeld et al.,1992, Cell, 68:143-155; Wilkinson et al., 1992, Nucl. Acids Res.,20:2233-2239; Stratford-Perricaudet et al., 1990, Hum. Gene Ther.,1:241-256), vaccinia virus (Mackett et al., 1992, Biotechnology,24:495-499), adeno-associated virus (Muzyczka, 1992, Curr. Top.Microbiol. Immunol., 158:91-123; On et al., 1990, Gene, 89:279-282),herpes viruses including HSV and EBV and CMV (Margolskee, 1992, Curr.Top. Microbiol. Immunol., 158:67-90; Johnson et al., 1992, J. Virol.,66:29522965; Fink et al., 1992, Hum. Gene Ther. 3:11-19; Breakfield etal., 1987, Mol. Neurobiol., 1:337-371; Fresse et al., 1990, Biochem.Pharmacol., 40:2189-2199), Sindbis viruses (H. Herweijer et al., 1995,Human Gene Therapy 6:1161-1167; U.S. Pat. Nos. 5,091,309 and5,2217,879), alphaviruses (S. Schlesinger, 1993, Trends Biotechnol.11:18-22; I. Frolov et al., 1996, Proc. Natl. Acad. Sci. USA93:11371-11377) and retroviruses of avian (Brandyopadhyay et al., 1984,Mol. Cell Biol., 4:749-754; Petropouplos et al., 1992, J. Virol.,66:3391-3397), murine (Miller, 1992, Curr. Top. Microbiol. Immunol.,158:1-24; Miller et al., 1985, Mol. Cell Biol., 5:431-437; Sorge et al.,1984, Mol. Cell Biol., 4:1730-1737; Mann et al., 1985, J. Virol.,54:401-407), and human origin (Page et al., 1990, J. Virol.,64:5370-5276; Buchschalcher et al., 1992, J. Virol., 66:2731-2739).Baculovirus (Autographa californica multinuclear polyhedrosis virus;AcMNPV) vectors are also known in the art, and may be obtained fromcommercial sources (such as PharMingen, San Diego, Calif.; ProteinSciences Corp., Meriden, Conn.; Stratagene, La Jolla, Calif.).Additional viral vectors are familiar to the person of ordinary skill inthe art.

In several embodiments, the methods and compositions disclosed hereininclude an adenoviral vector that expresses a recombinant RSV F proteinstabilized in a prefusion conformation. Adenovirus from various origins,subtypes, or mixture of subtypes can be used as the source of the viralgenome for the adenoviral vector. Non-human adenovirus (e.g., simian,chimpanzee, gorilla, avian, canine, ovine, or bovine adenoviruses) canbe used to generate the adenoviral vector. For example, a simianadenovirus can be used as the source of the viral genome of theadenoviral vector. A simian adenovirus can be of serotype 1, 3, 7, 11,16, 18, 19, 20, 27, 33, 38, 39, 48, 49, 50, or any other simianadenoviral serotype. A simian adenovirus can be referred to by using anysuitable abbreviation known in the art, such as, for example, SV, SAdV,SAV or sAV. In some examples, a simian adenoviral vector is a simianadenoviral vector of serotype 3, 7, 11, 16, 18, 19, 20, 27, 33, 38, or39. In one example, a chimpanzee serotype C Ad3 vector is used (see,e.g., Peruzzi et al., Vaccine, 27:1293-1300, 2009). Human adenovirus canbe used as the source of the viral genome for the adenoviral vector.Human adenovirus can be of various subgroups or serotypes. For instance,an adenovirus can be of subgroup A (e.g., serotypes 12, 18, and 31),subgroup B (e.g., serotypes 3, 7, 11, 14, 16, 21, 34, 35, and 50),subgroup C (e.g., serotypes 1, 2, 5, and 6), subgroup D (e.g., serotypes8, 9, 10, 13, 15, 17, 19, 20, 22, 23, 24, 25, 26, 27, 28, 29, 30, 32,33, 36-39, and 42-48), subgroup E (e.g., serotype 4), subgroup F (e.g.,serotypes 40 and 41), an unclassified serogroup (e.g., serotypes 49 and51), or any other adenoviral serotype. The person of ordinary skill inthe art is familiar with replication competent and deficient adenoviralvectors (including singly and multiply replication deficient adenoviralvectors). Examples of replication-deficient adenoviral vectors,including multiply replication-deficient adenoviral vectors, aredisclosed in U.S. Pat. Nos. 5,837,511; 5,851,806; 5,994,106; 6,127,175;6,482,616; and 7,195,896, and International Patent Application Nos. WO94/28152, WO 95/02697, WO 95/16772, WO 95/34671, WO 96/22378, WO97/12986, WO 97/21826, and WO 03/022311.

E. Compositions

The disclosed PreF antigens, viral vectors, and nucleic acid moleculescan be included in a pharmaceutical composition, including therapeuticand prophylactic formulations, and can be combined together with one ormore adjuvants and, optionally, other therapeutic ingredients, such asantiviral drugs. In several embodiments, compositions including one ormore of the disclosed PreF antigens, viral vectors, or nucleic acidmolecules are immunogenic compositions. The composition can include anyof the PreF antigens including a recombinant RSV F protein as disclosedherein, (such as a protein nanoparticle including any of the recombinantRSV F proteins as disclosed herein), a virus-like particle including anyof the recombinant RSV F proteins as disclosed herein, a nucleic acidmolecule encoding any of the recombinant RSV F proteins as disclosedherein, or a vector encoding or including any of the recombinant RSV Fproteins as disclosed herein.

In some embodiments, the composition includes a first isolated antigenincluding a recombinant RSV F protein stabilized in a prefusionconformation by any of the substitutions disclosed herein (such asS155C, S290C, and S190F substitutions or S155C, S290C, S190F, and V207Lsubstitutions), wherein the stabilized RSV F protein is based on asubtype A RSV F protein, and a second isolated antigen including arecombinant RSV F protein stabilized in a prefusion conformation by anyof the substitutions disclosed herein (such as S155C, S290C, and S190Fsubstitutions or S155C, S290C, S190F, and V207L substitutions), whereinthe stabilized RSV F protein is based on a subtype B RSV F protein.

In some embodiments, the composition includes a first proteinnanoparticle including a recombinant RSV F protein stabilized in aprefusion conformation by any of the substitutions disclosed herein(such as S155C, S290C, and S190F substitutions or S155C, S290C, S190F,and V207L substitutions), wherein the stabilized RSV F protein is basedon a subtype A RSV F protein, and a second protein nanoparticleincluding a recombinant RSV F protein stabilized in a prefusionconformation by any of the substitutions disclosed herein (such asS155C, S290C, and S190F substitutions or S155C, S290C, S190F, and V207Lsubstitutions), wherein the stabilized RSV F protein is based on asubtype B RSV F protein.

In some embodiments, the composition includes a first viral vectorincluding a recombinant RSV F protein stabilized in a prefusionconformation by any of the substitutions disclosed herein (such asS155C, S290C, and S190F substitutions or S155C, S290C, S190F, and V207Lsubstitutions), wherein the stabilized RSV F protein is based on asubtype A RSV F protein, and a second viral vector including arecombinant RSV F protein stabilized in a prefusion conformation by anyof the substitutions disclosed herein (such as S155C, S290C, and S190Fsubstitutions or S155C, S290C, S190F, and V207L substitutions), whereinthe stabilized RSV F protein is based on a subtype B RSV F protein.

In some embodiments, the composition includes a first virus-likeparticle including a recombinant RSV F protein stabilized in a prefusionconformation by any of the substitutions disclosed herein (such asS155C, S290C, and S190F substitutions or S155C, S290C, S190F, and V207Lsubstitutions), wherein the stabilized RSV F protein is based on asubtype A RSV F protein, and a second virus-like particle including arecombinant RSV F protein stabilized in a prefusion conformation by anyof the substitutions disclosed herein (such as S155C, S290C, and S190Fsubstitutions or S155C, S290C, S190F, and V207L substitutions), whereinthe stabilized RSV F protein is based on a subtype B RSV F protein.

In some embodiments, the composition includes a first nucleic acidmolecule (such as an expression vector) encoding a recombinant RSV Fprotein stabilized in a prefusion conformation by any of thesubstitutions disclosed herein (such as S155C, S290C, and S190Fsubstitutions or S155C, S290C, S190F, and V207L substitutions), whereinthe stabilized RSV F protein is based on a subtype A RSV F protein, anda second nucleic acid molecule (such as an expression vector) includinga recombinant RSV F protein stabilized in a prefusion conformation byany of the substitutions disclosed herein (such as S155C, S290C, andS190F substitutions or S155C, S290C, S190F, and V207L substitutions),wherein the stabilized RSV F protein is based on a subtype B RSV Fprotein.

Such pharmaceutical compositions can be administered to subjects by avariety of administration modes known to the person of ordinary skill inthe art, for example, nasal, pulmonary, intramuscular, subcutaneous,intravenous, intraperitoneal, or parenteral routes.

To formulate the compositions, the disclosed PreF antigens, viralvectors, or nucleic acid molecules can be combined with variouspharmaceutically acceptable additives, as well as a base or vehicle fordispersion of the conjugate. Desired additives include, but are notlimited to, pH control agents, such as arginine, sodium hydroxide,glycine, hydrochloric acid, citric acid, and the like. In addition,local anesthetics (for example, benzyl alcohol), isotonizing agents (forexample, sodium chloride, mannitol, sorbitol), adsorption inhibitors(for example, TWEEN® 80), solubility enhancing agents (for example,cyclodextrins and derivatives thereof), stabilizers (for example, serumalbumin), and reducing agents (for example, glutathione) can beincluded. Adjuvants, such as aluminum hydroxide (ALHYDROGEL®, availablefrom Brenntag Biosector, Copenhagen, Denmark and AMPHOGEL®, WyethLaboratories, Madison, NJ), Freund's adjuvant, MPL™ (3-O-deacylatedmonophosphoryl lipid A; Corixa, Hamilton, IN), IL-12 (GeneticsInstitute, Cambridge, MA) TLR agonists (such as TLR-9 agonists), amongmany other suitable adjuvants well known in the art, can be included inthe compositions.

When the composition is a liquid, the tonicity of the formulation, asmeasured with reference to the tonicity of 0.9% (w/v) physiologicalsaline solution taken as unity, is typically adjusted to a value atwhich no substantial, irreversible tissue damage will be induced at thesite of administration. Generally, the tonicity of the solution isadjusted to a value of about 0.3 to about 3.0, such as about 0.5 toabout 2.0, or about 0.8 to about 1.7.

The disclosed PreF antigens, viral vectors, or nucleic acid moleculescan be dispersed in a base or vehicle, which can include a hydrophiliccompound having a capacity to disperse the antigens, and any desiredadditives. The base can be selected from a wide range of suitablecompounds, including but not limited to, copolymers of polycarboxylicacids or salts thereof, carboxylic anhydrides (for example, maleicanhydride) with other monomers (for example, methyl (meth)acrylate,acrylic acid and the like), hydrophilic vinyl polymers, such aspolyvinyl acetate, polyvinyl alcohol, polyvinylpyrrolidone, cellulosederivatives, such as hydroxymethylcellulose, hydroxypropylcellulose andthe like, and natural polymers, such as chitosan, collagen, sodiumalginate, gelatin, hyaluronic acid, and nontoxic metal salts thereof.Often, a biodegradable polymer is selected as a base or vehicle, forexample, polylactic acid, poly(lactic acid-glycolic acid) copolymer,polyhydroxybutyric acid, poly(hydroxybutyric acid-glycolic acid)copolymer and mixtures thereof. Alternatively or additionally, syntheticfatty acid esters such as polyglycerin fatty acid esters, sucrose fattyacid esters and the like can be employed as vehicles. Hydrophilicpolymers and other vehicles can be used alone or in combination, andenhanced structural integrity can be imparted to the vehicle by partialcrystallization, ionic bonding, cross-linking and the like. The vehiclecan be provided in a variety of forms, including fluid or viscoussolutions, gels, pastes, powders, microspheres and films, for examplesfor direct application to a mucosal surface.

The disclosed PreF antigens, viral vectors, or nucleic acid moleculescan be combined with the base or vehicle according to a variety ofmethods, and release of the antigens can be by diffusion, disintegrationof the vehicle, or associated formation of water channels. In somecircumstances, the disclosed antigens, or a nucleic acid or a viralvector encoding, expressing or including the antigen, is dispersed inmicrocapsules (microspheres) or nanocapsules (nanospheres) prepared froma suitable polymer, for example, isobutyl 2-cyanoacrylate (see, forexample, Michael et al., J. Pharmacy Pharmacol. 43:1-5, 1991), anddispersed in a biocompatible dispersing medium, which yields sustaineddelivery and biological activity over a protracted time.

The pharmaceutical compositions can contain as pharmaceuticallyacceptable vehicles substances as required to approximate physiologicalconditions, such as pH adjusting and buffering agents, tonicityadjusting agents, wetting agents and the like, for example, sodiumacetate, sodium lactate, sodium chloride, potassium chloride, calciumchloride, sorbitan monolaurate, and triethanolamine oleate. For solidcompositions, conventional nontoxic pharmaceutically acceptable vehiclescan be used which include, for example, pharmaceutical grades ofmannitol, lactose, starch, magnesium stearate, sodium saccharin, talcum,cellulose, glucose, sucrose, magnesium carbonate, and the like.

Pharmaceutical compositions for administering the disclosed PreFantigens, viral vectors, or nucleic acid molecules can also beformulated as a solution, microemulsion, or other ordered structuresuitable for high concentration of active ingredients. The vehicle canbe a solvent or dispersion medium containing, for example, water,ethanol, polyol (for example, glycerol, propylene glycol, liquidpolyethylene glycol, and the like), and suitable mixtures thereof.Proper fluidity for solutions can be maintained, for example, by the useof a coating such as lecithin, by the maintenance of a desired particlesize in the case of dispersible formulations, and by the use ofsurfactants. In many cases, it will be desirable to include isotonicagents, for example, sugars, polyalcohols, such as mannitol andsorbitol, or sodium chloride in the composition. Prolonged absorption ofthe disclosed antigens can be brought about by including in thecomposition an agent which delays absorption, for example, monostearatesalts and gelatin.

In certain embodiments, the disclosed PreF antigens, viral vectors, ornucleic acid molecules can be administered in a time-releaseformulation, for example in a composition that includes a slow releasepolymer. These compositions can be prepared with vehicles that willprotect against rapid release, for example a controlled release vehiclesuch as a polymer, microencapsulated delivery system or bioadhesive gel.Prolonged delivery in various compositions of the disclosure can bebrought about by including in the composition agents that delayabsorption, for example, aluminum monostearate hydrogels and gelatin.When controlled release formulations are desired, controlled releasebinders suitable for use in accordance with the disclosure include anybiocompatible controlled release material which is inert to the activeagent and which is capable of incorporating the disclosed antigen and/orother biologically active agent. Numerous such materials are known inthe art. Useful controlled-release binders are materials that aremetabolized slowly under physiological conditions following theirdelivery (for example, at a mucosal surface, or in the presence ofbodily fluids). Appropriate binders include, but are not limited to,biocompatible polymers and copolymers well known in the art for use insustained release formulations. Such biocompatible compounds arenon-toxic and inert to surrounding tissues, and do not triggersignificant adverse side effects, such as nasal irritation, immuneresponse, inflammation, or the like. They are metabolized into metabolicproducts that are also biocompatible and easily eliminated from thebody. Numerous systems for controlled delivery of therapeutic proteinsare known (e.g., U.S. Pat. Nos. 5,055,303; 5,188,837; 4,235,871;4,501,728; 4,837,028; 4,957,735; and 5,019,369; 5,055,303; 5,514,670;5,413,797; 5,268,164; 5,004,697; 4,902,505; 5,506,206; 5,271,961;5,254,342; and 5,534,496).

Exemplary polymeric materials for use include, but are not limited to,polymeric matrices derived from copolymeric and homopolymeric polyestershaving hydrolyzable ester linkages. A number of these are known in theart to be biodegradable and to lead to degradation products having no orlow toxicity. Exemplary polymers include polyglycolic acids andpolylactic acids, poly(DL-lactic acid-co-glycolic acid), poly(D-lacticacid-co-glycolic acid), and poly(L-lactic acid-co-glycolic acid). Otheruseful biodegradable or bioerodable polymers include, but are notlimited to, such polymers as poly(epsilon-caprolactone),poly(epsilon-aprolactone-CO-lactic acid),poly(epsilon.-aprolactone-CO-glycolic acid), poly(beta-hydroxy butyricacid), poly(alkyl-2-cyanoacrilate), hydrogels, such as poly(hydroxyethylmethacrylate), polyamides, poly(amino acids) (for example, L-leucine,glutamic acid, L-aspartic acid and the like), poly(ester urea),poly(2-hydroxyethyl DL-aspartamide), polyacetal polymers,polyorthoesters, polycarbonate, polymaleamides, polysaccharides, andcopolymers thereof. Many methods for preparing such formulations arewell known to those skilled in the art (see, for example, Sustained andControlled Release Drug Delivery Systems, J. R. Robinson, ed., MarcelDekker, Inc., New York, 1978). Other useful formulations includecontrolled-release microcapsules (U.S. Pat. Nos. 4,652,441 and4,917,893), lactic acid-glycolic acid copolymers useful in makingmicrocapsules and other formulations (U.S. Pat. Nos. 4,677,191 and4,728,721) and sustained-release compositions for water-soluble peptides(U.S. Pat. No. 4,675,189).

Pharmaceutical compositions typically are sterile and stable underconditions of manufacture, storage and use. Sterile solutions can beprepared by incorporating the disclosed PreF antigens, viral vectors, ornucleic acid molecules in the required amount in an appropriate solventwith one or a combination of ingredients enumerated herein, as required,followed by filtered sterilization. Generally, dispersions are preparedby incorporating the disclosed antigen and/or other biologically activeagent into a sterile vehicle that contains a basic dispersion medium andthe required other ingredients from those enumerated herein. In the caseof sterile powders, methods of preparation include vacuum drying andfreeze-drying which yields a powder of the disclosed antigen plus anyadditional desired ingredient from a previously sterile-filteredsolution thereof. The prevention of the action of microorganisms can beaccomplished by various antibacterial and antifungal agents, forexample, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, andthe like.

Actual methods for preparing administrable compositions will be known orapparent to those skilled in the art and are described in more detail insuch publications as Remingtons Pharmaceutical Sciences, 19^(th) Ed.,Mack Publishing Company, Easton, Pennsylvania, 1995.

In several embodiments, the compositions include an adjuvant. The personof ordinary skill in the art is familiar with adjuvants, for example,those that can be included in an immunogenic composition. In severalembodiments, the adjuvant is selected to elicit a Th1 biased immuneresponse in a subject administered an immunogenic composition containingthe adjuvant and a disclosed antigens, or a nucleic acid or a viralvector encoding, expressing or including the antigen.

One suitable adjuvant is a non-toxic bacterial lipopolysaccharidederivative. An example of a suitable non-toxic derivative of lipid A, ismonophosphoryl lipid A or more particularly 3-Deacylated monophoshoryllipid A (3D-MPL). See, for example, U.S. Pat. Nos. 4,436,727; 4,877,611;4,866,034 and 4,912,094. 3D-MPL primarily promotes CD4+ T cell responseswith an IFN-γ (Th1) phenotype. 3D-MPL can be produced according to themethods disclosed in GB2220211 Å. Chemically it is a mixture of3-deacylated monophosphoryl lipid A with 3, 4, 5 or 6 acylated chains.In the compositions, small particle 3D-MPL can be used. Small particle3D-MPL has a particle size such that it can be sterile-filtered througha 0.22 m filter. Such preparations are described in WO94/21292.

In other embodiments, the lipopolysaccharide can be a β(1-6) glucosaminedisaccharide, as described in U.S. Pat. No. 6,005,099 and EP Patent No.0 729 473 B1. One of skill in the art would be readily able to producevarious lipopolysaccharides, such as 3D-MPL, based on the teachings ofthese references. In addition to the aforementioned immunostimulants(that are similar in structure to that of LPS or MPL or 3D-MPL),acylated monosaccharide and disaccharide derivatives that are asub-portion to the above structure of MPL are also suitable adjuvants.

In several embodiments, a Toll-like receptor (TLR) agonist is used as anadjuvant. For example a disclosed PreF antigen can be combined with aTLR agonist in an immunogenic composition used for elicitation of aneutralizing immune response to RSV. For example, the TLR agonist can bea TLR-4 agonist such as a synthetic derivative of lipid A (see, e.g., WO95/14026, and WO 01/46127) an alkyl Glucosaminide phosphate (AGP; see,e.g., WO 98/50399 or U.S. Pat. Nos. 6,303,347; 6,764,840). Othersuitable TLR-4 ligands, capable of causing a signaling response throughTLR-4 are, for example, lipopolysaccharide from gram-negative bacteriaand its derivatives, or fragments thereof, in particular a non-toxicderivative of LPS (such as 3D-MPL). Other suitable TLR agonists are:heat shock protein (HSP) 10, 60, 65, 70, 75 or 90; surfactant Protein A,hyaluronan oligosaccharides, heparan sulphate fragments, fibronectinfragments, fibrinogen peptides and β-defensin-2, and muramyl dipeptide(MDP). In one embodiment the TLR agonist is HSP 60, 70 or 90. Othersuitable TLR-4 ligands are as described in WO 2003/011223 and in WO2003/099195.

Additional TLR agonists (such as an agent that is capable of causing asignaling response through a TLR signaling pathway) are also useful asadjuvants, such as agonists for TLR2, TLR3, TLR7, TLR8 and/or TLR9.Accordingly, in one embodiment, the composition further includes anadjuvant which is selected from the group consisting of: a TLR-1agonist, a TLR-2 agonist, TLR-3 agonist, a TLR-4 agonist, TLR-5 agonist,a TLR-6 agonist, TLR-7 agonist, a TLR-8 agonist, TLR-9 agonist, or acombination thereof.

In one embodiment, a TLR agonist is used that is capable of causing asignaling response through TLR-1, for example one or more of from:Tri-acylated lipopeptides (LPs); phenol-soluble modulin; Mycobacteriumtuberculosis LP;S-(2,3-bis(palmitoyloxy)-(2-RS)-propyl)-N-palmitoyl-(R)-Cys-(S)-Ser-(S)-L-ys(4)-OH,trihydrochloride (Pam3Cys) LP which mimics the acetylated amino terminusof a bacterial lipoprotein and OspA LP from Borrelia burgdorferi. Inanother embodiment, a TLR agonist is used that is capable of causing asignaling response through TLR-2, such as one or more of a lipoprotein,a peptidoglycan, a bacterial lipopeptide from M tuberculosis, Bburgdorferi or T pallidum; peptidoglycans from species includingStaphylococcus aureus; lipoteichoic acids, mannuronic acids, Neisseriaporins, bacterial fimbriae, Yersina virulence factors, CMV virions,measles haemagglutinin, and zymosan from yeast. In some embodiments, aTLR agonist is used that is capable of causing a signaling responsethrough TLR-3, such as one or more of double stranded RNA (dsRNA), orpolyinosinic-polycytidylic acid (Poly IC), a molecular nucleic acidpattern associated with viral infection. In further embodiments, a TLRagonist is used that is capable of causing a signaling response throughTLR-5, such as bacterial flagellin. In additional embodiments, a TLRagonist is used that is capable of causing a signaling response throughTLR-6, such as one or more of mycobacterial lipoprotein, di-acylated LP,and phenol-soluble modulin. Additional TLR6 agonists are described in WO2003/043572. In an embodiment, a TLR agonist is used that is capable ofcausing a signaling response through TLR-7, such as one or more of asingle stranded RNA (ssRNA), loxoribine, a guanosine analogue atpositions N7 and C8, or an imidazoquinoline compound, or derivativethereof. In one embodiment, the TLR agonist is imiquimod. Further TLR7agonists are described in WO 2002/085905. In some embodiments, a TLRagonist is used that is capable of causing a signaling response throughTLR-8. Suitably, the TLR agonist capable of causing a signaling responsethrough TLR-8 is a single stranded RNA (ssRNA), an imidazoquinolinemolecule with anti-viral activity, for example resiquimod (R848);resiquimod is also capable of recognition by TLR-7. Other TLR-8 agonistswhich can be used include those described in WO 2004/071459.

In further embodiments, an adjuvant includes a TLR agonist capable ofinducing a signaling response through TLR-9. For example, the adjuvantcan include HSP90, bacterial or viral DNA, and/or DNA containingunmethylated CpG nucleotides (e.g., a CpG oligonucleotide). For example,CpG-containing oligonucleotides induce a predominantly Th1 response.Such oligonucleotides are well known and are described, for example, inWO 95/26204, WO 96/02555, WO 99/33488 and U.S. Pat. Nos. 5,278,302,5,666,153, and. 6,008,200 and 5,856,462. Accordingly, oligonucleotidesfor use as adjuvants in the disclosed compositions include CpGcontaining oligonucleotides, for example, containing two or moredinucleotide CpG motifs. Also included are oligonucleotides with mixedinternucleotide linkages.

Other adjuvants that can be used in immunogenic compositions with theantigens, or a nucleic acid or a viral vector encoding, expressing orincluding an antigen, e.g., on their own or in combination with 3D-MPL,or another adjuvant described herein, are saponins, such as QS21. Insome examples, saponins are used as an adjuvant, e.g., for systemicadministration of a PreF antigen. Use of saponins (e.g., use of Quil A,derived from the bark of the South American tree Quillaja SaponariaMolina) as adjuvants is familiar to the person of ordinary skill in theart (see, e.g., U.S. Pat. No. 5,057,540 and EP 0 362 279 B1. EP 0 109942 B1; WO 96/11711; WO 96/33739). The haemolytic saponins QS21 and QS17(HPLC purified fractions of Quil A) have been described as potentsystemic adjuvants, and the method of their production is disclosed inU.S. Pat. No. 5,057,540 and EP 0 362 279 B1.

The adjuvant can also include mineral salts such as an aluminum orcalcium salts, in particular aluminum hydroxide, aluminum phosphate andcalcium phosphate.

Another class of suitable Th1 biasing adjuvants for use in compositionsincludes outer membrane proteins (OMP)-based immunostimulatorycompositions. OMP-based immunostimulatory compositions are particularlysuitable as mucosal adjuvants, e.g., for intranasal administration.OMP-based immunostimulatory compositions are a genus of preparations of(OMPs, including some porins) from Gram-negative bacteria, e.g.,Neisseria species, which are useful as a carrier or in compositions forimmunogens, such as bacterial or viral antigens (see, e.g., U.S. Pat.Nos. 5,726,292; 4,707,543). Further, proteosomes have the capability toauto-assemble into vesicle or vesicle-like OMP clusters of about 20 nmto about 800 nm, and to noncovalently incorporate, coordinate, associate(e.g., electrostatically or hydrophobically), or otherwise cooperatewith protein antigens (Ags), particularly antigens that have ahydrophobic moiety. Proteosomes can be prepared, for example, asdescribed in the art (see, e.g., U.S. Pat. No. 5,726,292 or U.S. Pat.No. 5,985,284; 2003/0044425.).

Proteosomes are composed primarily of chemically extracted outermembrane proteins (OMPs) from Neisseria meningitidis (mostly porins Aand B as well as class 4 OMP), maintained in solution by detergent(Lowell G H. Proteosomes for Improved Nasal, Oral, or InjectableVaccines. In: Levine M M, Woodrow G C, Kaper J B, Cobon G S, eds, NewGeneration Vaccines. New York: Marcel Dekker, Inc. 1997; 193-206).Proteosomes can be formulated with a variety of antigens such aspurified or recombinant proteins derived from viral sources, includingthe PreF polypeptides disclosed herein. The gradual removal of detergentallows the formation of particulate hydrophobic complexes ofapproximately 100-200 nm in diameter (Lowell G H. Proteosomes forImproved Nasal, Oral, or Injectable Vaccines. In: Levine M M, Woodrow GC, Kaper J B, Cobon G S, eds, New Generation Vaccines. New York: MarcelDekker, Inc. 1997; 193-206).

Combinations of different adjuvants can also be used in compositionswith the disclosed PreF antigens, viral vectors, or nucleic acidmolecules in the composition. For example, as already noted, QS21 can beformulated together with 3D-MPL. The ratio of QS21:3D-MPL will typicallybe in the order of 1:10 to 10:1; such as 1:5 to 5:1, and oftensubstantially 1:1. Typically, the ratio is in the range of 2.5:1 to 1:13D-MPL:QS21 (such as AS01 (GlaxoSmithKline). Another combinationadjuvant formulation includes 3D-MPL and an aluminum salt, such asaluminum hydroxide (such as AS04 (GlaxoSmithKline). When formulated incombination, this combination can enhance an antigen-specific Th1 immuneresponse.

In some instances, the adjuvant formulation a mineral salt, such as acalcium or aluminum (alum) salt, for example calcium phosphate, aluminumphosphate or aluminum hydroxide. In some embodiments, the adjuvantincludes an oil and water emulsion, e.g., an oil-in-water emulsion (suchas MF59 (Novartis) or AS03 (GlaxoSmithKline). One example of anoil-in-water emulsion comprises a metabolisable oil, such as squalene, atocol such as a tocopherol, e.g., alpha-tocopherol, and a surfactant,such as sorbitan trioleate (Span 85) or polyoxyethylene sorbitanmonooleate (Tween 80), in an aqueous carrier.

The pharmaceutical composition typically contains a therapeuticallyeffective amount of a disclosed PreF antigen, viral vector, or nucleicacid molecule and can be prepared by conventional techniques.Preparation of immunogenic compositions, including those foradministration to human subjects, is generally described inPharmaceutical Biotechnology, Vol. 61 Vaccine Design—the subunit andadjuvant approach, edited by Powell and Newman, Plenum Press, 1995. NewTrends and Developments in Vaccines, edited by Voller et al., UniversityPark Press, Baltimore, Maryland, U.S.A. 1978. Encapsulation withinliposomes is described, for example, by Fullerton, U.S. Pat. No.4,235,877. Conjugation of proteins to macromolecules is disclosed, forexample, by Likhite, U.S. Pat. No. 4,372,945 and by Armor et al., U.S.Pat. No. 4,474,757. Typically, the amount of antigen in each dose of theimmunogenic composition is selected as an amount which induces an immuneresponse without significant, adverse side effects.

The amount of the disclosed PreF antigen, viral vector, or nucleic acidmolecule can vary depending upon the specific antigen employed, theroute and protocol of administration, and the target population, forexample. Typically, each human dose will comprise 1-1000 μg of protein,such as from about 1 μg to about 100 μg, for example, from about 1 μg toabout 50 μg, such as about 1 μg, about 2 μg, about 5 μg, about 10 μg,about 15 μg, about 20 μg, about 25 μg, about 30 μg, about 40 μg, orabout 50 μg. The amount utilized in an immunogenic composition isselected based on the subject population (e.g., infant or elderly). Anoptimal amount for a particular composition can be ascertained bystandard studies involving observation of antibody titers and otherresponses in subjects. It is understood that a therapeutically effectiveamount of an antigen in a immunogenic composition can include an amountthat is ineffective at eliciting an immune response by administration ofa single dose, but that is effective upon administration of multipledosages, for example in a prime-boost administration protocol.

In several examples, pharmaceutical compositions for eliciting an immuneresponse against RSV in humans include a therapeutically effectiveamount of a disclosed PreF antigens, viral vectors, or nucleic acidmolecules for administration to infants (e.g., infants between birth and1 year, such as between 0 and 6 months, at the age of initial dose) orelderly patients subject (such as a subject greater than 65 years ofage). It will be appreciated that the choice of adjuvant can bedifferent in these different applications, and the optimal adjuvant andconcentration for each situation can be determined empirically by thoseof skill in the art.

In certain embodiments, the pharmaceutical compositions are vaccinesthat reduce or prevent infection with RSV. In some embodiments, theimmunogenic compositions are vaccines that reduce or prevent apathological response following infection with RSV. Optionally, thepharmaceutical compositions containing the disclosed PreF antigen, viralvector, or nucleic acid molecule are formulated with at least oneadditional antigen of a pathogenic organism other than RSV. For example,the pathogenic organism can be a pathogen of the respiratory tract (suchas a virus or bacterium that causes a respiratory infection). In certaincases, the pharmaceutical composition contains an antigen derived from apathogenic virus other than RSV, such as a virus that causes aninfection of the respiratory tract, such as influenza or parainfluenza.In other embodiments, the additional antigens are selected to facilitateadministration or reduce the number of inoculations required to protecta subject against a plurality of infectious organisms. For example, theantigen can be derived from any one or more of influenza, hepatitis B,diphtheria, tetanus, pertussis, Hemophilus influenza, poliovirus,Streptococcus or Pneumococcus, among others.

F. Methods of Treatment

In several embodiments, the disclosed PreF antigens, or a nucleic acidor a viral vector encoding, expressing or including a PreF antigen areused to induce an immune response to RSV in a subject. Thus, in severalembodiments, a therapeutically effective amount of an immunogeniccomposition including one or more of the disclosed PreF antigens, or anucleic acid or a viral vector encoding, expressing or including theantigen, can be administered to a subject in order to generate an immuneresponse to RSV.

In accordance with the disclosure herein, a prophylactically ortherapeutically effective amount of a immunogenic composition includinga PreF antigen, or a nucleic acid or a viral vector encoding, expressingor including the antigen, is administered to a subject in need of suchtreatment for a time and under conditions sufficient to prevent,inhibit, and/or ameliorate a RSV infection in a subject. The immunogeniccomposition is administered in an amount sufficient to elicit an immuneresponse against an RSV antigen, such as RSV F protein, in the subject.

In some embodiments, the composition administered to the subjectincludes (or encodes) a first recombinant RSV F protein that is asubtype A RSV F protein stabilized in a prefusion conformation, and asecond recombinant RSV F protein that is a subtype B RSV F proteinstabilized in a prefusion conformation. In several embodiments, thecomposition administered to the subject includes a mixture (such asabout a 1:1, 1:2, 2:1, 2:3, 3:2, 1:3, 3:1, 1:4, 4:1, 3:5, 5:3, 1:5, 5:1,5:7, 7:5 mixture), of a first recombinant RSV F protein that is asubtype A RSV F protein stabilized in a prefusion conformation, and asecond recombinant RSV F protein that is a subtype B RSV F proteinstabilized in a prefusion conformation.

In some embodiments the composition administered to the subject includesa first protein nanoparticle including a recombinant RSV F proteinstabilized in a prefusion conformation by any of the substitutionsdisclosed herein (such as S155C, S290C, and S190F substitutions orS155C, S290C, S190F, and V207L substitutions), wherein the stabilizedRSV F protein is based on a subtype A RSV F protein, and a secondprotein nanoparticle including a recombinant RSV F protein stabilized ina prefusion conformation by any of the substitutions disclosed herein(such as S155C, S290C, and S190F substitutions or S155C, S290C, S190F,and V207L substitutions), wherein the stabilized RSV F protein is basedon a subtype B RSV F protein.

In some embodiments the composition administered to the subject includesa first nucleic acid molecule (such as an expression vector) encoding arecombinant RSV F protein stabilized in a prefusion conformation by anyof the substitutions disclosed herein (such as S155C, S290C, and S190Fsubstitutions or S155C, S290C, S190F, and V207L substitutions), whereinthe stabilized RSV F protein is based on a subtype A RSV F protein, anda second nucleic acid molecule (such as an expression vector) includinga recombinant RSV F protein stabilized in a prefusion conformation byany of the substitutions disclosed herein (such as S155C, S290C, andS190F substitutions or S155C, S290C, S190F, and V207L substitutions),wherein the stabilized RSV F protein is based on a subtype B RSV Fprotein.

In some embodiments, a composition including ferritin nanoparticlesincluding the recombinant RSV F protein stabilized in a prefusionconformation by any of the substitutions disclosed herein (such asS155C, S290C, and S190F substitutions or S155C, S290C, S190F, and V207Lsubstitutions) is administered to a subject. In some embodiments thecomposition administered to the subject includes a first ferritinnanoparticle including a recombinant RSV F protein stabilized in aprefusion conformation by any of the substitutions disclosed herein(such as S155C, S290C, and S190F substitutions or S155C, S290C, S190F,and V207L substitutions), wherein the stabilized RSV F protein is basedon a subtype A RSV F protein, and a second ferritin nanoparticleincluding a recombinant RSV F protein stabilized in a prefusionconformation by any of the substitutions disclosed herein (such asS155C, S290C, and S190F substitutions or S155C, S290C, S190F, and V207Lsubstitutions), wherein the stabilized RSV F protein is based on asubtype B RSV F protein. Methods of making ferritin nanoparticlesincluding a viral antigen and their use for immunization purposes (e.g.,for immunization against influenza antigens) have been disclosed in theart (see, e.g., Kanekiyo et al., Nature, 499:102-106, 2013, incorporatedby reference herein in its entirety).

In some embodiments, a subject is selected for treatment that has, or isat risk for developing, an RSV infection, for example, because ofexposure or the possibility of exposure to RSV. Following administrationof a therapeutically effective amount of the disclosed therapeuticcompositions, the subject can be monitored for RSV infection, symptomsassociated with RSV infection, or both. Because nearly all humans areinfected with RSV by the age of 3, the entire birth cohort is includedas a relevant population for immunization. This could be done, forexample, by beginning an immunization regimen anytime from birth to 6months of age, from 6 months of age to 5 years of age, in pregnant women(or women of child-bearing age) to protect their infants by passivetransfer of antibody, family members of newborn infants or those stillin utero, and subjects greater than 50 years of age.

Subjects at greatest risk of RSV infection with severe symptoms (e.g.requiring hospitalization) include children with prematurity,bronchopulmonary dysplasia, and congenital heart disease are mostsusceptible to severe disease. Atopy or a family history of atopy hasalso been associated with severe disease in infancy. During childhoodand adulthood, disease is milder but can be associated with lower airwaydisease and is commonly complicated by sinusitis. Disease severityincreases in the institutionalized elderly (e.g., humans over 65 yearsold). Severe disease also occurs in persons with severe combinedimmunodeficiency disease or following bone marrow or lungtransplantation. (See, e.g., Shay et al., JAMA, 282:1440-6, 1999; Hallet al., N Engl J Med. 2009; 360:588-598; Glezen et al., Am J Dis Child.,1986; 140:543-546; and Graham, Immunol. Rev., 239:149-166, 2011, each ofwhich is incorporated by reference herein). Thus, these subjects can beselected for administration of the disclosed PreF antigens, or a nucleicacid or a viral vector encoding, expressing or including a PreF antigen.

Typical subjects intended for treatment with the compositions andmethods of the present disclosure include humans, as well as non-humanprimates and other animals, such as cattle. To identify subjects forprophylaxis or treatment according to the methods of the disclosure,screening methods employed to determine risk factors associated with atargeted or suspected disease or condition, or to determine the statusof an existing disease or condition in a subject. These screeningmethods include, for example, conventional work-ups to determineenvironmental, familial, occupational, and other such risk factors thatmay be associated with the targeted or suspected disease or condition,as well as diagnostic methods, such as various ELISA and otherimmunoassay methods, which are available and well known in the art todetect and/or characterize RSV infection. These and other routinemethods allow the clinician to select patients in need of therapy usingthe methods and pharmaceutical compositions of the disclosure. Animmunogenic composition can be administered as an independentprophylaxis or treatment program, or as a follow-up, adjunct orcoordinate treatment regimen to other treatments.

The immunogenic composition can be used in coordinate vaccinationprotocols or combinatorial formulations. In certain embodiments,combinatorial immunogenic compositions and coordinate immunizationprotocols employ separate immunogens or formulations, each directedtoward eliciting an immune response to an RSV antigen, such as an immuneresponse to RSV F protein. Separate immunogenic compositions that elicitthe immune response to the RSV antigen can be combined in a polyvalentimmunogenic composition administered to a subject in a singleimmunization step, or they can be administered separately (in monovalentimmunogenic compositions) in a coordinate immunization protocol.

The administration of the immunogenic compositions can be for eitherprophylactic or therapeutic purpose. When provided prophylactically, theimmunogenic composition is provided in advance of any symptom, forexample in advance of infection. The prophylactic administration of theimmunogenic compositions serves to prevent or ameliorate any subsequentinfection. When provided therapeutically, the immunogenic composition isprovided at or after the onset of a symptom of disease or infection, forexample after development of a symptom of RSV infection, or afterdiagnosis of RSV infection. The immunogenic composition can thus beprovided prior to the anticipated exposure to RSV so as to attenuate theanticipated severity, duration or extent of an infection and/orassociated disease symptoms, after exposure or suspected exposure to thevirus, or after the actual initiation of an infection.

Administration induces a sufficient immune response to treat or preventthe pathogenic infection, for example, to inhibit the infection and/orreduce the signs and/or symptoms of the infection. Amounts effective forthis use will depend upon the severity of the disease, the general stateof the subject's health, and the robustness of the subject's immunesystem. A therapeutically effective amount of the disclosed immunogeniccompositions is that which provides either subjective relief of asymptom(s) or an objectively identifiable improvement as noted by theclinician or other qualified observer.

For prophylactic and therapeutic purposes, the immunogenic compositioncan be administered to the subject in a single bolus delivery, viacontinuous delivery (for example, continuous transdermal, mucosal orintravenous delivery) over an extended time period, or in a repeatedadministration protocol (for example, by an hourly, daily or weekly,repeated administration protocol). The therapeutically effective dosageof the immunogenic composition can be provided as repeated doses withina prolonged prophylaxis or treatment regimen that will yield clinicallysignificant results to alleviate one or more symptoms or detectableconditions associated with a targeted disease or condition as set forthherein. Determination of effective dosages in this context is typicallybased on animal model studies followed up by human clinical trials andis guided by administration protocols that significantly reduce theoccurrence or severity of targeted disease symptoms or conditions in thesubject. Suitable models in this regard include, for example, murine,rat, porcine, feline, ferret, non-human primate, and other acceptedanimal model subjects known in the art. Alternatively, effective dosagescan be determined using in vitro models (for example, immunologic andhistopathologic assays). Using such models, only ordinary calculationsand adjustments are required to determine an appropriate concentrationand dose to administer a therapeutically effective amount of theimmunogenic composition (for example, amounts that are effective toelicit a desired immune response or alleviate one or more symptoms of atargeted disease). In alternative embodiments, an effective amount oreffective dose of the immunogenic composition may simply inhibit orenhance one or more selected biological activities correlated with adisease or condition, as set forth herein, for either therapeutic ordiagnostic purposes.

In one embodiment, a suitable immunization regimen includes at leastthree separate inoculations with one or more immunogenic compositions,with a second inoculation being administered more than about two, aboutthree to eight, or about four, weeks following the first inoculation.Generally, the third inoculation is administered several months afterthe second inoculation, and in specific embodiments, more than aboutfive months after the first inoculation, more than about six months toabout two years after the first inoculation, or about eight months toabout one year after the first inoculation. Periodic inoculations beyondthe third are also desirable to enhance the subject's “immune memory.”The adequacy of the vaccination parameters chosen, e.g., formulation,dose, regimen and the like, can be determined by taking aliquots ofserum from the subject and assaying antibody titers during the course ofthe immunization program. If such monitoring indicates that vaccinationis sub-optimal, the subject can be boosted with an additional dose ofimmunogenic composition, and the vaccination parameters can be modifiedin a fashion expected to potentiate the immune response. It iscontemplated that there can be several boosts, and that each boost caninclude the same or a different PreF antigen.

For prime-boost protocols, the prime can be administered as a singledose or multiple doses, for example two doses, three doses, four doses,five doses, six doses or more can be administered to a subject overdays, weeks or months. The boost can be administered as a single dose ormultiple doses, for example two to six doses, or more can beadministered to a subject over a day, a week or months. Multiple boostscan also be given, such one to five, or more. Different dosages can beused in a series of sequential inoculations. For example a relativelylarge dose in a primary inoculation and then a boost with relativelysmaller doses. The immune response against the selected antigenicsurface can be generated by one or more inoculations of a subject withan immunogenic composition disclosed herein.

In some embodiments, the prime composition administered to the subjectincludes (or encodes) a recombinant RSV F protein that is a subtype ARSV F protein stabilized in a prefusion conformation, and the boostcomposition administered to the subject includes (or encodes) arecombinant RSV F protein that is a subtype B RSV F protein stabilizedin a prefusion conformation. In some embodiments, the prime compositionadministered to the subject includes (or encodes) a recombinant RSV Fprotein that is a subtype B RSV F protein stabilized in a prefusionconformation, and the boost composition administered to the subjectincludes (or encodes) a recombinant RSV F protein that is a subtype ARSV F protein stabilized in a prefusion conformation.

In some embodiments, the methods include administering a compositionincluding a recombinant subtype A RSV F protein stabilized in aprefusion conformation and a recombinant subtype B RSV F proteinstabilized in a prefusion conformation once, or more than one (such asin a prime-boost protocol) as a series of injections.

In some embodiments, the methods include administering a compositionincluding a ferritin nanoparticle including a recombinant subtype A RSVF protein stabilized in a prefusion conformation and ferritinnanoparticle including a recombinant subtype B RSV F protein stabilizedin a prefusion conformation, once, or more than one (such as in aprime-boost protocol) as a series of injections.

In some embodiments, the methods include administering a compositionincluding a vector encoding a recombinant subtype A RSV F proteinstabilized in a prefusion conformation and vector encoding a recombinantsubtype B RSV F protein stabilized in a prefusion conformation, once, ormore than one (such as in a prime-boost protocol) as a series ofinjections. In some embodiments, the method can further includeadministration of a composition including recombinant subtype A RSV Fprotein stabilized in a prefusion conformation and recombinant subtype BRSV F protein stabilized in a prefusion conformation, and/or acomposition including a ferritin nanoparticle including a recombinantsubtype A RSV F protein stabilized in a prefusion conformation andferritin nanoparticle including a recombinant subtype B RSV F proteinstabilized in a prefusion conformation.

In some embodiments, the methods include administering a compositionincluding a nucleic acid molecule encoding a recombinant subtype A RSV Fprotein stabilized in a prefusion conformation and nucleic acid moleculeencoding a recombinant subtype B RSV F protein stabilized in a prefusionconformation once, or more than one (such as in a prime-boost protocol)as a series of injections. In some embodiments, the method can furtherinclude administration of a composition including recombinant subtype ARSV F protein stabilized in a prefusion conformation and recombinantsubtype B RSV F protein stabilized in a prefusion conformation, and/or acomposition including a ferritin nanoparticle including a recombinantsubtype A RSV F protein stabilized in a prefusion conformation andferritin nanoparticle including a recombinant subtype B RSV F proteinstabilized in a prefusion conformation.

In some embodiments, the prime and boost compositions administered tothe subject each include (or encode) a first recombinant RSV F proteinthat is a subtype A RSV F protein stabilized in a prefusionconformation, and a second recombinant RSV F protein that is a subtype BRSV F protein stabilized in a prefusion conformation. In severalembodiments, the prime and boost compositions administered to thesubject each include (or encode) a mixture (such as about a 1:1, 1:2,2:1, 2:3, 3:2, 1:3, 3:1, 1:4, 4:1, 3:5, 5:3, 1:5, 5:1, 5:7, 7:5mixture), of a first recombinant RSV F protein that is a subtype A RSV Fprotein stabilized in a prefusion conformation, and a second recombinantRSV F protein that is a subtype B RSV F protein stabilized in aprefusion conformation.

In some embodiments the prime and boost compositions administered to thesubject each include a recombinant RSV F protein that is a subtype A RSVF protein stabilized in a prefusion conformation by any of thesubstitutions disclosed herein (such as S155C, S290C, and S190Fsubstitutions or S155C, S290C, S190F, and V207L substitutions), and asecond recombinant RSV F protein that is a subtype B RSV F proteinstabilized in a prefusion conformation by any of the substitutionsdisclosed herein (such as S155C, S290C, and S190F substitutions orS155C, S290C, S190F, and V207L substitutions).

In some embodiments the prime and boost compositions administered to thesubject each include a nucleic acid molecule encoding a recombinant RSVF protein that is a subtype A RSV F protein stabilized in a prefusionconformation by any of the substitutions disclosed herein (such asS155C, S290C, and S190F substitutions or S155C, S290C, S190F, and V207Lsubstitutions), and a nucleic acid molecule encoding a recombinant RSV Fprotein that is a subtype B RSV F protein stabilized in a prefusionconformation by any of the substitutions disclosed herein (such asS155C, S290C, and S190F substitutions or S155C, S290C, S190F, and V207Lsubstitutions).

In some embodiments the prime and boost compositions administered to thesubject each include a first protein nanoparticle (such as a ferritinnanoparticle) including a recombinant RSV F protein that is a subtype ARSV F protein stabilized in a prefusion conformation by any of thesubstitutions disclosed herein (such as S155C, S290C, and S190Fsubstitutions or S155C, S290C, S190F, and V207L substitutions), and asecond protein nanoparticle (such as a ferritin nanoparticle) includinga recombinant RSV F protein that is a subtype B RSV F protein stabilizedin a prefusion conformation by any of the substitutions disclosed herein(such as S155C, S290C, and S190F substitutions or S155C, S290C, S190F,and V207L substitutions).

In some embodiments the prime and boost compositions administered to thesubject each include a vector including or encoding a recombinant RSV Fprotein that is a subtype A RSV F protein stabilized in a prefusionconformation by any of the substitutions disclosed herein (such asS155C, S290C, and S190F substitutions or S155C, S290C, S190F, and V207Lsubstitutions), and a vector including or encoding a recombinant RSV Fprotein that is a subtype B RSV F protein stabilized in a prefusionconformation by any of the substitutions disclosed herein (such asS155C, S290C, and S190F substitutions or S155C, S290C, S190F, and V207Lsubstitutions).

In some embodiments the prime composition administered to the subjectincludes a first nucleic acid molecule (such as a DNA plasmid expressionvector) encoding a recombinant RSV F protein that is a subtype A RSV Fprotein stabilized in a prefusion conformation by any of thesubstitutions disclosed herein (such as S155C, S290C, and S190Fsubstitutions or S155C, S290C, S190F, and V207L substitutions), and asecond nucleic acid molecule (such as an expression vector) including arecombinant RSV F protein that is a subtype B RSV F protein stabilizedin a prefusion conformation by any of the substitutions disclosed herein(such as S155C, S290C, and S190F substitutions or S155C, S290C, S190F,and V207L substitutions), and the boost composition administered to thesubject includes a first protein nanoparticle (such as a ferritinnanoparticle) including a recombinant RSV F protein that is a subtype ARSV F protein stabilized in a prefusion conformation by any of thesubstitutions disclosed herein (such as S155C, S290C, and S190Fsubstitutions or S155C, S290C, S190F, and V207L substitutions), and asecond protein nanoparticle (such as a ferritin nanoparticle) includinga recombinant RSV F protein that is a subtype B RSV F protein stabilizedin a prefusion conformation by any of the substitutions disclosed herein(such as S155C, S290C, and S190F substitutions or S155C, S290C, S190F,and V207L substitutions).

Immunization protocols using a DNA plasmid prime and ferritinnanoparticle boost are known to the person of ordinary skill in the art(see, e.g., Wei et al., Science, 329(5995):1060-4, 2010, which isincorporated by reference herein in its entirety).

The actual dosage of the immunogenic composition will vary according tofactors such as the disease indication and particular status of thesubject (for example, the subject's age, size, fitness, extent ofsymptoms, susceptibility factors, and the like), time and route ofadministration, other drugs or treatments being administeredconcurrently, as well as the specific pharmacology of the immunogeniccomposition for eliciting the desired activity or biological response inthe subject. Dosage regimens can be adjusted to provide an optimumprophylactic or therapeutic response. As described above in the forgoinglisting of terms, an effective amount is also one in which any toxic ordetrimental side effects of the disclosed antigen and/or otherbiologically active agent is outweighed in clinical terms bytherapeutically beneficial effects.

A non-limiting range for a therapeutically effective amount of thedisclosed PreF antigens within the methods and immunogenic compositionsof the disclosure is about 0.0001 mg/kg body weight to about 10 mg/kgbody weight, such as about 0.01 mg/kg, about 0.02 mg/kg, about 0.03mg/kg, about 0.04 mg/kg, about 0.05 mg/kg, about 0.06 mg/kg, about 0.07mg/kg, about 0.08 mg/kg, about 0.09 mg/kg, about 0.1 mg/kg, about 0.2mg/kg, about 0.3 mg/kg, about 0.4 mg/kg, about 0.5 mg/kg, about 0.6mg/kg, about 0.7 mg/kg, about 0.8 mg/kg, about 0.9 mg/kg, about 1 mg/kg,about 1.5 mg/kg, about 2 mg/kg, about 2.5 mg/kg, about 3 mg/kg, about 4mg/kg, about 5 mg/kg, or about 10 mg/kg, for example 0.01 mg/kg to about1 mg/kg body weight, about 0.05 mg/kg to about 5 mg/kg body weight,about 0.2 mg/kg to about 2 mg/kg body weight, or about 1.0 mg/kg toabout 10 mg/kg body weight.

In some embodiments, the dosage a set amount of a disclosed PreFantigen, or a nucleic acid or a viral vector encoding, expressing orincluding a PreF antigen includes for children, adults, elderly, etc.,such as from about 1-300 μg, for example, a dosage of about 1, 2, 3, 4,5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200,250, or about 300 μg of the PreF antigens, or a nucleic acid or a viralvector encoding, expressing or including a PreF antigen. The dosage andnumber of doses will depend on the setting, for example, in an adult oranyone primed by prior RSV infection or immunization, a single dose maybe a sufficient booster. In naïve infants, in some examples, at leasttwo doses would be given, for example, at least three doses. In someembodiments, an annual boost is given to elderly subjects (e.g., humansover age 60) once per year, for example, along with an annual influenzavaccination. Methods for preparing administrable compositions will beknown or apparent to those skilled in the art and are described in moredetail in such publications as Remingtons Pharmaceutical Sciences,19^(th) Ed., Mack Publishing Company, Easton, Pennsylvania, 1995.

Dosage can be varied by the attending clinician to maintain a desiredconcentration at a target site (for example, systemic circulation).Higher or lower concentrations can be selected based on the mode ofdelivery, for example, trans-epidermal, rectal, oral, pulmonary, orintranasal delivery versus intravenous or subcutaneous delivery. Dosagecan also be adjusted based on the release rate of the administeredformulation, for example, of an intrapulmonary spray versus powder,sustained release oral versus injected particulate or transdermaldelivery formulations, and so forth. To achieve the same serumconcentration level, for example, slow-release particles with a releaserate of 5 nanomolar (under standard conditions) would be administered atabout twice the dosage of particles with a release rate of 10 nanomolar.

Upon administration of an immunogenic composition of this disclosure,the immune system of the subject typically responds to the immunogeniccomposition by producing antibodies specific for the prefusionconformation of the RSV F protein. Such a response signifies that aneffective dose of the immunogenic composition was delivered.

In several embodiments, it may be advantageous to administer theimmunogenic compositions disclosed herein with other agents such asproteins, peptides, antibodies, and other antiviral agents, such asanti-RSV agents. Non-limiting examples of anti-RSV agents include themonoclonal antibody palivizumab (SYNAGIS®; Medimmune, Inc.) and thesmall molecule anti-viral drug ribavirin (manufactured by many sources,e.g., Warrick Pharmaceuticals, Inc.). In certain embodiments,immunogenic compositions are administered concurrently with otheranti-RSV agents. In certain embodiments, the immunogenic compositionsare administered sequentially with other anti-RSV therapeutic agents,such as before or after the other agent. One of ordinary skill in theart would know that sequential administration can mean immediatelyfollowing or after an appropriate period of time, such as hours, days,weeks, months, or even years later.

In additional embodiments, a therapeutically effective amount of apharmaceutical composition including a nucleic acid encoding a disclosedPreF antigen is administered to a subject in order to generate an immuneresponse. In one specific, non-limiting example, a therapeuticallyeffective amount of a nucleic acid encoding a disclosed antigen isadministered to a subject to treat or prevent or inhibit RSV infection.

One approach to administration of nucleic acids is direct immunizationwith plasmid DNA, such as with a mammalian expression plasmid. Asdescribed above, the nucleotide sequence encoding a disclosed antigencan be placed under the control of a promoter to increase expression ofthe molecule. Another approach would use RNA (such as Nonviral deliveryof self-amplifying RNA vaccines, see e.g., Geall et al., Proc Natl AcadSci USA, 109:14604-9, 2012.

Immunization by nucleic acid constructs is well known in the art andtaught, for example, in U.S. Pat. No. 5,643,578 (which describes methodsof immunizing vertebrates by introducing DNA encoding a desired antigento elicit a cell-mediated or a humoral response), and U.S. Pat. Nos.5,593,972 and 5,817,637 (which describe operably linking a nucleic acidsequence encoding an antigen to regulatory sequences enablingexpression). U.S. Pat. No. 5,880,103 describes several methods ofdelivery of nucleic acids encoding immunogenic peptides or otherantigens to an organism. The methods include liposomal delivery of thenucleic acids (or of the synthetic peptides themselves), andimmune-stimulating constructs, or ISCOMS™, negatively charged cage-likestructures of 30-40 nm in size formed spontaneously on mixingcholesterol and Quil A™ (saponin). Protective immunity has beengenerated in a variety of experimental models of infection, includingtoxoplasmosis and Epstein-Barr virus-induced tumors, using ISCOMS™ asthe delivery vehicle for antigens (Mowat and Donachie, Immunol. Today12:383, 1991). Doses of antigen as low as 1 μg encapsulated in ISCOMS™have been found to produce Class I mediated CTL responses (Takahashi etal., Nature 344:873, 1990).

In another approach to using nucleic acids for immunization, a disclosedantigen can also be expressed by attenuated viral hosts or vectors orbacterial vectors. Recombinant vaccinia virus, adenovirus,adeno-associated virus (AAV), herpes virus, retrovirus, cytomegalovirusor other viral vectors can be used to express the peptide or protein,thereby eliciting a CTL response. For example, vaccinia vectors andmethods useful in immunization protocols are described in U.S. Pat. No.4,722,848. BCG (Bacillus Calmette Guerin) provides another vector forexpression of the peptides (see Stover, Nature 351:456-460, 1991).

In one embodiment, a nucleic acid encoding a disclosed PreF antigen isintroduced directly into cells. For example, the nucleic acid can beloaded onto gold microspheres by standard methods and introduced intothe skin by a device such as Bio-Rad's HELIOS™ Gene Gun. The nucleicacids can be “naked,” consisting of plasmids under control of a strongpromoter. Typically, the DNA is injected into muscle, although it canalso be injected directly into other sites, including tissues inproximity to metastases. Dosages for injection are usually around 0.5μg/kg to about 50 mg/kg, and typically are about 0.005 mg/kg to about 5mg/kg (see, e.g., U.S. Pat. No. 5,589,466).

In addition to the therapeutic methods provided above, any of thedisclosed PreF antigens can be utilized to produce antigen specificimmunodiagnostic reagents, for example, for serosurveillance.Immunodiagnostic reagents can be designed from any of the antigensdescribed herein. For example, in the case of the disclosed antigens,the presence of serum antibodies to RSV is monitored using the isolatedantigens disclosed herein, such as to detect an RSV infection and/or thepresence of antibodies that specifically bind to the prefusionconformation of RSV F protein.

Generally, the method includes contacting a sample from a subject, suchas, but not limited to a blood, serum, plasma, urine or sputum samplefrom the subject with one or more of the RSV F protein antigenstabilized in a prefusion conformation disclosed herein and detectingbinding of antibodies in the sample to the disclosed immunogens. Thebinding can be detected by any means known to one of skill in the art,including the use of labeled secondary antibodies that specifically bindthe antibodies from the sample. Labels include radiolabels, enzymaticlabels, and fluorescent labels.

In addition, the detection of the prefusion RSV F binding antibody alsoallows the response of the subject to immunization with the disclosedantigen to be monitored. In still other embodiments, the titer of theprefusion RSV F antibody binding antibodies is determined. The bindingcan be detected by any means known to one of skill in the art, includingthe use of labeled secondary antibodies that specifically bind theantibodies from the sample. Labels include radiolabels, enzymaticlabels, and fluorescent labels. In other embodiments, a disclosedimmunogen is used to isolate antibodies present in a subject orbiological sample obtained from a subject.

G. Kits

Kits are also provided. For example, kits for treating or preventing anRSV infection in a subject, or for detecting the presence of RSV Fprotein prefusion specific antibodies in the sera of a subject. The kitswill typically include one or more of the PreF antigens, or a nucleicacid or a viral vector encoding, expressing or including the antigen.

The kit can include a container and a label or package insert on orassociated with the container. Suitable containers include, for example,bottles, vials, syringes, etc. The containers may be formed from avariety of materials such as glass or plastic. The container typicallyholds a composition including one or more of the disclosed PreFantigens, or a nucleic acid or a viral vector encoding, expressing orincluding the antigen, which is effective for treating or preventing RSVinfection. In several embodiments the container may have a sterileaccess port (for example the container may be an intravenous solutionbag or a vial having a stopper pierceable by a hypodermic injectionneedle). The label or package insert indicates that the composition isused for treating the particular condition.

The label or package insert typically will further include instructionsfor use of a PreF antigen, or a nucleic acid or a viral vector encoding,expressing or including the antigen, for example, in a method oftreating or preventing a RSV infection. The package insert typicallyincludes instructions customarily included in commercial packages oftherapeutic products that contain information about the indications,usage, dosage, administration, contraindications and/or warningsconcerning the use of such therapeutic products. The instructionalmaterials may be written, in an electronic form (such as a computerdiskette or compact disk) or may be visual (such as video files). Thekits may also include additional components to facilitate the particularapplication for which the kit is designed. The kits may additionallyinclude buffers and other reagents routinely used for the practice of aparticular method. Such kits and appropriate contents are well known tothose of skill in the art.

H. Certain Embodiments

Additional embodiments are disclosed in section H on pages 135-158 ofpriority U.S. Provisional application No. 61/863,909, filed Aug. 8,2013, which is specifically incorporated by reference herein in itsentirety.

-   -   Clause 1. An isolated immunogen, comprising:    -   a recombinant RSV F protein or fragment thereof comprising at        least one amino acid substitution compared to a native RSV F        protein that stabilizes the recombinant RSV F protein in a        prefusion conformation that specifically binds to a RSV F        prefusion specific antibody, and wherein the antibody does not        specifically bind to a RSV F protein in a post-fusion        conformation.    -   Clause 2. the immunogen specifically binds to the antibody after        incubation at 20° C. in phosphate buffered saline at        physiological pH for at least 24 hours in the absence of the        antibody.    -   Clause 3. The immunogen of clause 1 or clause 2, wherein the        prefusion conformation of the recombinant RSV F protein or        fragment thereof comprises an antigenic site Ø that specifically        binds to the prefusion specific antibody, and wherein the        antigenic site Ø comprises residues 62-69 and 196-209 of a        native RSV F protein sequence set forth as one of SEQ ID NOs:        1-184.    -   Clause 4. The immunogen of any of clauses 1-3, wherein the        immunogen specifically binds to a D25, a AM22, a 5C4, or a MPE8        prefusion specific antibody.    -   Clause 5. The immunogen of any of clauses 1-4, wherein the        native RSV F protein is a human subtype A, human subtype B, or        bovine RSV F protein.    -   Clause 6. The immunogen of any of clauses 1-5, wherein the        recombinant RSV F protein or fragment thereof comprises a F₁        polypeptide and a F₂ polypeptide, and optionally does not        comprise a pep27 polypeptide or portion thereof.    -   Clause 7. The immunogen of clause 6, wherein the F₂ and F₁        polypeptides comprise RSV F positions 62-69 and 196-209,        respectively, and wherein:    -   the F₂ polypeptide comprises or consists of 8-84 residues of RSV        F positions 26-109; and    -   the F₁ polypeptides comprises or consists of 14-393 residues of        RSV F positions 137-529,    -   wherein the RSV F positions correspond to the amino acid        sequence of a reference F₀ polypeptide set forth as SEQ ID NO:        124.    -   Clause 8. The immunogen of clause 7, wherein the C-terminal        residue of the F₂ polypeptide and the N-terminal residue of the        F₁ polypeptide, respectively, comprise RSV F positions 97 and        137; 97 and 145; 97 and 150; 102 and 144; 102 and 145; 102 and        146; 102 and 147; 103 and 144; 103 and 145; 103 and 146; 103 and        147; 104 and 144; 104 and 145; 104 and 146; 104 and 147; 105 and        144; 105 and 145; 105 and 146; 105 and 147; or 105 and 150.    -   Clause 9. The immunogen of clause 7, wherein the F₂ and F₁        polypeptides respectively comprise or consist of RSV F        positions: 26-109 and 137-513; 26-107 and 137-513; 26-107 and        145-513; 26-105 and 137-513; 26-105 and 145-513; 26-103 and        145-513; 26-109 and 137-529; 26-107 and 137-529; 26-107 and        145-529; 26-105 and 137-529; 26-105 and 145-529; 26-103 and        145-529; 46-103 and 147-310; 46-104 and 146-310; 50-96 and        149-306; 51-103 and 146-307; 51-103 and 139-307; 50-105 and        146-306; or 53-97 and 148 to one of 305-320.    -   Clause 10. The immunogen of any of the preceding clauses,        wherein the recombinant RSV F protein comprises or consists of a        F₂ polypeptide and a F₁ polypeptide comprising amino acid        sequences at least 80% identical to amino acids 26-103 and        145-310, respectively, of a native RSV F protein sequence set        forth as any one of SEQ ID NOs: 1-184.    -   Clause 11. The immunogen of any of the preceding clauses,        wherein the recombinant RSV F protein comprises or consists of a        F₂ polypeptide and a F₁ polypeptide comprising amino acid        sequences at least 80% identical to amino acids 26-103 and        145-310, respectively, of SEQ ID NO: 124.    -   Clause 12 The immunogen of any of the preceding clauses, wherein        the recombinant RSV F protein comprises or consists of a F₂        polypeptide and a F₁ polypeptide comprising amino acid sequences        at least 80% identical to amino acids 26-103 and 145-513,        respectively, of SEQ ID NO: 124.    -   Clause 13. The immunogen of any of the preceding clauses,        wherein the recombinant RSV F protein comprises or consists of a        F₂ polypeptide and a F₁ polypeptide comprising amino acid        sequences at least 80% identical to amino acids 26-103 and        145-529, respectively, of SEQ ID NO: 124.    -   Clause 14. The immunogen of any of the preceding clauses,        wherein the recombinant RSV F protein comprises or consists of a        F₂ polypeptide and a F₁ polypeptide comprising amino acid        sequences at least 80% identical to amino acids 26-103 and        145-551, respectively, of SEQ ID NO: 124.    -   Clause 15. The immunogen of any of the preceding clauses,        wherein the recombinant RSV F protein is a single chain RSV F        protein and the F₂ and F₁ polypeptides are linked by a        heterologous peptide linker, or are directly linked.    -   Clause 16. The immunogen of clause 15, wherein    -   position 105 of the F₂ polypeptide is linked to position 145 of        the F₁ polypeptide by a Gly-Ser linker; or    -   position 103 of the F₂ polypeptide is directly linked to        position 145 of the F₁ polypeptide.    -   Clause 17. The immunogen of clause 16 or clause 16, wherein the        heterologous peptide linker comprises the amino acid sequence        set forth as one of SEQ ID NOs: 356-365 or 1443-1453, or is a G,        S, GG, GS, SG, GGG, or GSG linker.    -   Clause 18. The isolated immunogen of any one of the previous        clauses, wherein the recombinant RSV F protein is stabilized in        the RSV F protein prefusion conformation by:    -   (a) a first disulfide bond between a pair of cysteines;    -   (b) a cavity-filling amino acid substitution;    -   (c) a repacking amino acid substitution;    -   (d) a N-linked glycosylation site;    -   (e) a combination of two or more of (a)-(d); or    -   (f) a combination of (a) and (b).    -   Clause 19. The isolated immunogen of clause 18, wherein wherein        the pair of cysteines comprises a first cysteine and a second        cysteine, and wherein    -   the first cysteine and the second cysteine are in positions        137-216 of the F₁ polypeptide;    -   the first cysteine and the second cysteine are in positions        461-513 of the F₁ polypeptide; or    -   the first cysteine and the second cysteine are in positions        137-216 and 461-513, respectively, of the F₁ polypeptide; and    -   wherein the amino acid positions correspond to the amino acid        sequence of a reference F₀ polypeptide set forth as SEQ ID NO:        124.    -   Clause 20. The immunogen of clause 18, wherein the first        cysteine is introduced by amino acid substitution onto one of        RSV F positions 137-216, and the second cysteine is introduced        by amino acid substitution onto one of RSV F positions 271-460.    -   Clause 21. The immunogen of clause 19 or clause 20, wherein the        pair of cysteines comprises a first cysteine and a second        cysteine, each comprising a Cα carbon and a CP carbon, and        wherein:    -   (a) the first cysteine is introduced by amino acid substitution        onto one of RSV F positions 137-216 or 461-513, and the second        cysteine is introduced by amino acid substitution onto one of        RSV F positions 26-61, 77-97, or 271-460; and    -   (b) the Cα carbon of the position of the first cysteine is from        2.0-8.0 angstroms from the Cα carbon of the position of the        second cysteine, and/or the Cβ carbon of the position of the        first cysteine is from 2.0-5.5 angstroms from the Cβ carbon of        the position of the second cysteine using an optimal rotomer for        each Cβ carbon, in the three-dimensional structure set forth by        the structural coordinates provided in Table 1.    -   Clause 22. The immunogen of clause 19 or clause 20, wherein the        pair of cysteines comprises a first cysteine and a second        cysteine, each comprising a Cα carbon and a CP carbon, and        wherein:    -   (a) the first cysteine and the second cysteine are introduced by        amino acid substitution onto RSV F positions 137-216 or RSV F        positions 461-513; or the first cysteine is introduced by amino        acid substitution onto RSV F positions 137-216, and the second        cysteine is introduced by amino acid substitution onto RSV F        positions 461-513; and    -   (b) the Cα carbon of the position of the first cysteine is from        2.0-8.0 angstroms from the Cα carbon of the position of the        second cysteine, and/or the Cβ carbon of the position of the        first cysteine is from 2.0-5.5 angstroms from the Cβ carbon of        the position of the second cysteine using an optimal rotomer for        each Cβ carbon, in the three-dimensional structure set forth by        the structural coordinates provided in Table 1.    -   Clause 23. The immunogen of clause 18, wherein the disulfide        bond comprises an intra-protomer or an inter-protomer disulfide        bond.    -   Clause 24. The immunogen of clause 23, wherein the non-natural        disulfide bond comprises    -   an intra-protomer disulfide bond between RSV F positions 155 and        290; 151 and 288; 137 and 337; 397 and 487; 138 and 353; 341 and        352; 403 and 420; 319 and 413; 401 and 417; 381 and 388; 320 and        415; 319 and 415; 331 and 401; 320 and 335; 406 and 413; 381 and        391; 357 and 371; 403 and 417; 321 and 334; 338 and 394; 288 and        300; 60 and 194; 33 and 469; 54 and 154; 59 and 192; 46 and 311;        48 and 308; or 30 and 410;    -   an inter-protomer disulfide bond between RSV F positions 400 and        489; 144 and 406; 153 and 461; 149 and 458; 143 and 404; 346 and        454; 399 and 494; 146 and 407; 374 and 454; 369 and 455; 402 and        141; 74 and 218; 183 and 428, and the recombinant RSV F protein        comprises a G insertion between positions 182/183; 183 and 428,        and the recombinant RSV F protein comprises a C insertion        between positions 427/428; 145 and 460, and the recombinant RSV        F protein comprises a AA insertion between positions 146/147;        183 and 423, and the recombinant RSV F protein comprises a AAA        insertion between positions 182/183; or 330 and 430, and the        recombinant RSV F protein comprises a CAA insertion between        positions 329/330;    -   the intra-protomer disulfide bond between RSV F positions 155        and 290, and wherein the recombinant RSV F protein comprises        further comprises a non-natural disulfide bond between RSV F        positions 74 and 218; 141 and 402; 146 and 460, and a G        insertion between positions 460/461; 345 and 454, and a C        insertion between positions 453/454; 374 and 454, and a C        insertion between positions 453/454; 239 and 279, and a C        insertion between positions 238/239; 330 and 493, and a C        insertion between positions 329/330; 183 and 428, and a G        insertion between positions 182/183; or 183 and 428, and a C        insertion between positions 427/428.    -   Clause 25. The immunogen of clause 23, wherein the recombinant        RSV F protein comprises:    -   the intra-protomer disulfide bond, and one or more of the        following sets of substitutions: S155C and S290C; G151C and        I288C; F137C and T337C; T397C and E487C; L138C and P353C; W341C        and F352C; S403C and T420C; S319C and I413C; D401C and Y417C;        L381C and N388C; P320C and S415C; S319C and S415C; N331C and        D401C; P320C and T335C; V406C and I413C; L381C and Y391C; T357C        and N371C; S403C and Y417C; L321C and L334C; D338C and K394C;        I288C and V300C; E60C and D194C; Y33C and V469C; T54C and V154C;        I59C and V192C; S46C and T311C; L48C and V308C; E30C and L410C;        or    -   the inter-protomer disulfide bond, and one or more of the        following sets of substitutions: T400C and D489C; V144C and        V406C; A153C and K461C; A149C and Y458C; G143C and S404C; S346C        and N454C; K399C and Q494C; S146C and I407C; T374C and N454C;        T369C and T455C; or V402C and L141C; A74C and E218C; S155C,        S290C, L141C, and V402C; S155C, S290C, A74C, and E218C; N183C        and N428C, and a G insertion between positions 182/183; N183C        and N427G, and a C insertion between positions 427/428; S145C        and 460C; and an AA insertion between positions 146/147; N183C        and K423C, and an AAA insertion between positions 182/183; A329C        and S430C, and a CAA insertion between positions 329/330; or    -   the intra-protomer disulfide bond between RSV F positions 155        and 290 and the additional non-natural disulfide bond, S155C and        S290C substitutions, and one or more of the following sets of        amino acid substitutions: S146C, and N460C, and a G insertion        between positions 460/461; N345C, and N454G, and a C insertion        between positions 453/454; T374C, and N454G, and a C insertion        between positions 453/454; S238G, and Q279C, and a C insertion        between positions 238/239; and S493C, and a C insertion between        positions 329/330; N183C, and N428C; and a G insertion between        positions 182/183; or N183C, and N427G; and a C insertion        between positions 427/428.    -   Clause 26. The immunogen of clause 23, wherein the recombinant        RSV F protein comprises    -   an F₁ polypeptide comprising the amino acid sequence set forth        as residues 137-513 of one of SEQ ID NOs: 185, 189, 201, 202,        205, 207, 209, 213, 244, 245, 247, 257-262, 264-275, 277-282,        284, 296-299, 302, 303, 338-340; or    -   an F₂ polypeptide and an F₁ polypeptide comprising the amino        acid sequences set forth as residues 26-109 and 137-513,        respectively, of one of SEQ ID NOs: 190, 211, 212, 243, 246,        263, 276, 283, 285.    -   wherein the amino acid positions correspond to the amino acid        sequence of a reference F₀ polypeptide set forth as SEQ ID NO:        124.    -   Clause 27. The immunogen of clause 23, wherein the non-natural        disulfide bond comprises an intra-protomer disulfide bond        between RSV F positions 155 and 290.    -   Clause 28. The immunogen of clause 23, wherein the recombinant        RSV F protein comprises S155C and S290C substitutions.    -   Clause 29. The immunogen of clause 23, wherein the recombinant        RSV F protein comprises or consists of an amino acid sequence        comprising at least 80% identity to residues 26-109 and 137-513,        residues 26-103 and 145-513, or residues 26-105 and 145-513, of        SEQ ID NOs: 185.    -   Clause 30. The immunogen of any of clauses 18-29, comprising the        cavity-filling amino acid substitution comprising a F, L, W, Y,        H, or M substitution at position 190, position 207, or positions        190 and 207.    -   Clause 31. The immunogen of any of clauses 18-29, comprising the        cavity-filling amino acid substitution comprising one of 190F;        190L; 190W; 190Y; 190H; 190M; 190F and 207L; 190F and 207F; 190F        and 207W; 190L and 207L; 190L and 207F; 190L and 207W; 190W and        207L; 190W and 207F; 190W and 207W; 190Y and 207L; 190Y and        207F; 190Y and 207W; 190H and 207L; 190H and 207F; 190H and        207W; 190M and 207L; 190M and 207F; 190M and 207W; 207L and        220L; 296F and 190F; 220L and 153W; 203W; 83W and 260W; 58W and        298L; or 87F and 90L.    -   Clause 32. The immunogen of clause 31, wherein the recombinant        RSV F protein comprises positions 137-513 of one of SEQ ID NOs:        191, 193, 196-197 or 248, or 371-376, or positions 26-109 and        137-513 of one of SEQ ID NOs: 192, 195, or 194.    -   Clause 33. The immunogen of clause 30, wherein the recombinant        RSV F protein comprises or consists of an amino acid sequence        comprising at least 80% identity to residues 26-109 and 137-513,        residues 26-103 and 145-513, or residues 26-105 and 145-513, of        SEQ ID NO: 191.    -   Clause 34. The immunogen of clause 18, wherein the recombinant        RSV F protein comprises a non-natural disulfide bond between        cysteine substitutions at position 155 and 290, and a cavity        filling F, L, W, Y, H, or M substitution at position 190,        position 207, or positions 190 and 207.    -   Clause 35. The immunogen of clause 18, wherein the recombinant        RSV F protein comprises S155C, S290C, and S190F substitutions,        or S155C, S290C, S190F, and V207L substitutions.    -   Clause 36. The immunogen of clause 18, wherein the recombinant        RSV F protein comprises or consists of an amino acid sequence        comprising at least 80% identity to residues 26-109 and 137-513,        respectively, or 26-103 and 145-513, respectfully, or 26-105 and        145-513, respectfully, of one of SEQ ID NOs: 185 (DS, subtype        A), 371 (DS-Cav1, subtype A), 372 (DSCav1, subtype B), 373        (DSCav1, bovine), 374 (DS S190F, subtype A), 375 (DS, S190F,        subtype B), or 376 (DS, S190F, bovine).    -   Clause 37. The immunogen of clause 18, wherein the recombinant        RSV F protein is stabilized in the RSV F protein prefusion        conformation by a repacking amino acid substitution, wherein the        F₁ polypeptide comprises the amino acid substitutions set forth        in one of: 64L, 79V, 86W, 193V, 195F, 198F, 199F, 203F, 207L,        and 214L; 64L, 79L, 86W, 193V, 195F, 198F, 199F, 203F, and 214L;        64W, 79V, 86W, 193V, 195F, 198F, 199F, 203F, 207L, and 214L;        79V, 86F, 193V, 195F, 198F, 199F, 203F, 207L, and 214L; 64V,        79V, 86W, 193V, 195F, 198F, 199Y, 203F, 207L, and 214L; 64F,        79V, 86W, 193V, 195F, 198F, 199F, 203F, 207L, and 214L; 64L,        79V, 86W, 193V, 195F, 199F, 203F, 207L, and 214L; 56I, 58I,        164I, 171I, 179L, 181F, 187I, 291V, 296I, and 298I; 56I, 58I,        164I, 179L, 189F, 291V, 296I, and 298I; 56L, 58I, 158W, 164L,        167V, 171I, 179L, 181F, 187I, 291V, and 296L; 56L, 58I, 158Y,        164L, 167V, 187I, 189F, 291V, and 296L; 56I, 58W, 164I, 167F,        171I, 179L, 181V, 187I, 291V, and 296I; 56I, 58I, 64L, 79V, 86W,        164I, 179L, 189F, 193V, 195F, 198F, 199F, 203F, 207L, 214L,        291V, 296I, and 298I; 56I, 58I, 79V, 86F, 164I, 179L, 189F,        193V, 195F, 198F, 199F, 203F, 207L, 214L, 291V, 296I, and 298I;        56I, 58W, 64L, 79V, 86W, 164I, 167F, 171I, 179L, 181V, 187I,        193V, 195F, 198F, 199F, 203F, 207L, 214L, 291V, and 296I; 56I,        58W, 79V, 86F, 164I, 167F, 171I, 179L, 181V, 187I, 193V, 195F,        198F, 199F, 203F, 207L, 214L, 291V, and 296I; 486N, 487Q, 489N,        and 491A; 486H, 487Q, and 489H; 400V, 486L, 487L, and 489L;        400V, 486I, 487L, and 489I; 400V, 485I, 486L, 487L, 489L, 494L,        and 498L; 400V, 485I, 486I, 487L, 489I, 494L, and 498L; 399I,        400V, 485I, 486L, 487L, 489L, 494L, 497L, and 498L; 399I, 400V,        485I, 486I, 487L, 489I, 494L, 497L, and 498L; 375W, 391F, and        394M; 375W, 391F, and 394W; 375W, 391F, 394M, 486N, 487Q, 489N,        and 491A; 375W, 391F, 394M, 486H, 487Q, and 489H; 375W, 391F,        394W, 486N, 487Q, 489N, and 491A; 375W, 391F, 394W, 486H, 487Q,        and 489H; 375W, 391F, 394M, 400V, 486L, 487L, 489L, 494L, and        498M; 375W, 391F, 394M, 400V, 486I, 487L, 489I, 494L, and 498M;        375W, 391F, 394W, 400V, 486L, 487L, 489L, 494L, and 498M; 375W,        391F, 394W, 400V, 486I, 487L, 489I, 494L, and 498M; 137W and        339M; 137W and 140W; 137W, 140W, and 488W; 486N, 487Q, 489N,        491A, and 488W; 486H, 487Q, 489H, and 488W; 400V, 486L, 487L,        489L, and 488W; 400V, 486I, 487L, 489I, and 488W; 486N, 487Q,        489N, 491A, 137W, and 140W; 486H, 487Q, 489H, 137W, and 140W;        400V, 486L, 487L, 489L, 137W, and 140W; 375W, 391F, 394M, 137W,        and 140W; or 375W, 391F, 394M, 137W, 140W, and 339M        substitutions; and wherein the amino acid positions correspond        to the amino acid sequence of a reference F₀ polypeptide set        forth as SEQ ID NO: 124.    -   Clause 38. The immunogen of clause 37, wherein the recombinant        RSV F protein is stabilized in the RSV F protein prefusion        conformation by the repacking amino acid substitution, wherein        the F₁ polypeptide comprises the amino acid substitutions set        forth in one of: I64L, I79V, Y86W, L193V, L195F, Y198F, I199F,        L203F, V207L, and I214L; I64L, I79L, Y86W, L193V, L195F, Y198F,        I199F, L203F, and I214L; I64W, I79V, Y86W, L193V, L195F, Y198F,        I199F, L203F, V207L, and I214L; I79V, Y86F, L193V, L195F, Y198F,        I199F, L203F, V207L, and I214L; I64V, I79V, Y86W, L193V, L195F,        Y198F, I199Y, L203F, V207L, and I214L; I64F, I79V, Y86W, L193V,        L195F, Y198F, I199F, L203F, V207L, and I214L; I64L, I79V, Y86W,        L193V, L195F, I199F, L203F, V207L, and I214L; V56I, T58I, V164I,        L171I, V179L, L181F, V187I, I291V, V296I, and A298I; V56I, T58I,        V164I, V179L, T189F, I291V, V296I, and A298I; V56L, T58I, L158W,        V164L, I167V, L171I, V179L, L181F, V187I, I291V, and V296L;        V56L, T58I, L158Y, V164L, I167V, V187I, T189F, I291V, and V296L;        V56I, T58W, V164I, I167F, L171I, V179L, L181V, V187I, I291V, and        V296I; V56I, T58I, I64L, I79V, Y86W, V164I, V179L, T189F, L193V,        L195F, Y198F, I199F, L203F, V207L, I214L, I291V, V296I, and        A298I; V56I, T58I, I79V, Y86F, V164I, V179L, T189F, L193V,        L195F, Y198F, I199F, L203F, V207L, I214L, I291V, V296I, and        A298I; V56I, T58W, I64L, I79V, Y86W, V164I, I167F, L171I, V179L,        L181V, V187I, L193V, L195F, Y198F, I199F, L203F, V207L, I214L,        I291V, and V296I; V56I, T58W, I79V, Y86F, V164I, I167F, L171I,        V179L, L181V, V187I, L193V, L195F, Y198F, I199F, L203F, V207L,        I214L, I291V, and V296I; D486N, E487Q, D489N, and S491A; D486H,        E487Q, and D489H; T400V, D486L, E487L, and D489L; T400V, D486I,        E487L, and D489I; T400V, S485I, D486L, E487L, D489L, Q494L, and        K498L; T400V, S485I, D486I, E487L, D489I, Q494L, and K498L;        K399I, T400V, S485I, D486L, E487L, D489L, Q494L, E497L, and        K498L; K399I, T400V, S485I, D486I, E487L, D489I, Q494L, E497L,        and K498L; L375W, Y391F, and K394M; L375W, Y391F, and K394W;        L375W, Y391F, K394M, D486N, E487Q, D489N, and S491A; L375W,        Y391F, K394M, D486H, E487Q, and D489H; L375W, Y391F, K394W,        D486N, E487Q, D489N, and S491A; L375W, Y391F, K394W, D486H,        E487Q, and D489H; L375W, Y391F, K394M, T400V, D486L, E487L,        D489L, Q494L, and K498M; L375W, Y391F, K394M, T400V, D486I,        E487L, D489I, Q494L, and K498M; L375W, Y391F, K394W, T400V,        D486L, E487L, D489L, Q494L, and K498M; L375W, Y391F, K394W,        T400V, D486I, E487L, D489I, Q494L, and K498M; F137W and R339M;        F137W and F140W; F137W, F140W, and F488W; D486N, E487Q, D489N,        S491A, and F488W; D486H, E487Q, D489H, and F488W; T400V, D486L,        E487L, D489L, and F488W; T400V, D486I, E487L, D489I, and F488W;        D486N, E487Q, D489N, S491A, F137W, and F140W; D486H, E487Q,        D489H, F137W, and F140W; T400V, D486L, E487L, D489L, F137W, and        F140W; L375W, Y391F, K394M, F137W, and F140W; or L375W, Y391F,        K394M, F137W, F140W, and R339M; and wherein the amino acid        positions correspond to the amino acid sequence of a reference        F₀ polypeptide set forth as SEQ ID NO: 124.    -   Clause 39. The immunogen of clause 38, wherein the recombinant        RSV F protein is stabilized in the RSV F protein prefusion        conformation by a repacking amino acid substitution, wherein the        F₁ polypeptide comprises positions 137-513 of one of SEQ ID NO:        227-242, 249-256, 286-295, or 326-337.    -   Clause 40. The immunogen of any of clauses 18-39, wherein the        recombinant RSV F protein is stabilized in the RSV F protein        prefusion conformation by a N-linked glycosylation site, wherein        the N-linked glycosylation site is at one of F₁ polypeptide        positions 506, 175, 178, 276, 476, 185, 160, 503, 157, or a        combination of two or more thereof, wherein the amino acid        positions correspond to the amino acid sequence of a reference        F₀ polypeptide set forth as SEQ ID NO: 124.    -   Clause 41. The immunogen of clause 40, wherein the recombinant        RSV F protein comprises one of (a) I506N and K508T; (b)        A177S; (c) V178N; (d) V278T; (e) Y478T; (f) V185N and V187T; (g)        L160N and G162S; (h) L503N and F505S; (i) V157N; (j) or a        combination of two or more of (a)-(j); and wherein the amino        acid positions correspond to the amino acid sequence of a        reference F₀ polypeptide set forth as SEQ ID NO: 124.    -   Clause 42. The immunogen of clause 41, wherein the recombinant        RSV F protein is stabilized in the RSV F protein prefusion        conformation by a N-linked glycosylation site, and wherein the        F₁ polypeptide comprises positions 137-513 of one of SEQ ID NOs:        198-200, 203-204, 214-217.    -   Clause 43. The immunogen of any one of clauses 18, wherein the        recombinant RSV F protein is stabilized in the RSV F protein        prefusion conformation comprises the amino acid substitutions        set forth as one of: S238C and E92C; L193C and I59C; I59C and        L297C; L297C and I292C; K176C and S190C; T189C and A177C; T58C        and K191C; A424C and V450C; L171C and K191C; K176C and S190C;        K77C and 1217C; K427C and D448C; G151C and N302C; G151C and        V300C; T189C and V56C; L171C and K191C; L230F; L158F; L230F and        L158F; L203F; V187F; Y198F; Y198W; L204F; Y53F and L188F; V187F        and L203F; Y198F and L203F; L141W; L142F; L142W; V144F; V144W;        V90F; L83F; V185F and T54A; I395F; V90F, V185F, and T54A; L83F        and V90F; L83F, V185F, and T54A; L230F, V90F, and I395F; I395F,        V185F, and T54A; L203F, V90F, L230F, L158F, S509F, I395F, V185F,        and T54A; I221Y; F140W; F137W; S190L and V192L; V187F, S190L,        and V192L; V187L, S190L, and V192L; V185F, V187L, S190L, and        V192L; V154L, V157L, V185L, and V187L; V154L, V185L, and V187L;        V187F; T58L A298L; T58L, V154L, V185L, V187L, and A298L; Y458W;        L158F and I167A; L158W and I167A; L158F; L158W; V56L, I167L, and        A298L; V56L, I167L, and A298M; V56L and A167L; I167F; I167M;        V154F; V56L, I167L, A298L, and V154F; I199L, L203F; I199L,        L203F, P205Q, and I206T; I199L, L203F, P205E, and I206K; I199L,        L203F, and V207F; I199L, L203F, P205Q, I206T, and V207F; I199L,        L203F, P205E, I206K, and V207F; I199L, L203F, and L83F; I199L,        L203F, P205Q, I206T, and L83F; I199L, L203F, P205E, I206K, and        L83F; I199L, L203F, S190L, and V192L; I199L, L203F, P205Q,        I206T, V187F, and S190L, V192L; S55A, S190M, L203F, V207I, and        V296I; Y53F, S55A, K176I, S190L, V207I, S259L, D263L, and V296I;        L158F, V207M, and V296I; V56L, V207M, and V296I; V56L, V207I,        and V296I; V56I, V207M, and V296I; V154L, V207M, and V296I;        Y198F, V207I, T219W, and V296I; Y198F, V207I, T219I, and V296I;        Y198F, V207M, T219W, and V296I; 198F, V207M, T219I, and V296I;        Y198F, V207M, T219L, and V296I; S190Y; S190W; I206F, V207M,        T219V, and V296I; Y198F, V207M, T219L, and K226M; Y198F, V207M,        T219L, and K226W; Y198F, V207M, T219L, and K226L; L158F, L203F,        V207I, and V296I; F488W; F488R; V207L; S190F; S190M; L503E,        I506K, and S509F; L503E, I506K, S509F, and F505W; L503E, I506K,        S509F, L230F, and L158F; Q279C, and S238C; Q501F; E82V, V207M,        N227L, and V296I; E82V, V207I, N227L, and V296I; L158F, Y198F,        V207M, S215G, N216P, and T219L; L158F, Y198F, V207M, S213G,        S215G, and T219L; V56L, E82V, L203F, V207M, N227L, L230F, and        V296I; E82V, L158F, L203F, V207M, N227L, L230F, and V296I; E82V,        L203F, V207M, K226M, N227L, L230F, and V296I; or L203F, V207I,        S180C, S186C, and V296I;    -   wherein the amino acid positions correspond to the amino acid        sequence of a reference F₀ polypeptide set forth as SEQ ID NO:        124.    -   Clause 44. The immunogen of clause 18, wherein the recombinant        RSV F protein comprises    -   S155C and S290C substitutions, and further comprises one of the        following sets of substitutions: L513C, 514E, and 515C; L513C,        514E, 515E, and 516C; L512C, 513E, and 514C; or L512C, 513E,        514E, and 515C;    -   S155C, S290C, and S190F substitutions, and further comprises one        of the following sets of substitutions: F488W, L513C, A514E, and        I515C; F488W, L513C, A514E, G515E, and 516C; F488W, L512C,        L513E, and A514C; F488W, L512C, L513E, A514E, and G515C; A424C,        V450C, L171C, K191C, F488W, L513C, A514E, and I515C; A424C,        V450C, L171C, K191C, F488W, L513C, A514E, G515E, and 516C;        A424C, V450C, L171C, K191C, F488W, L512C, L513E, and A514C;        A424C, V450C, L171C, K191C, F488W, L512C, L513E, A514E, and        G515C; K77C, I217C, A424C, V450C, L171C, K191C, F488W, L513C,        L514E, and A515C; K77C, I217C, A424C, V450C, L171C, K191C,        F488W, L513C, L514E, and A515E; K77C, I217C, A424C, V450C,        L171C, K191C, F488W, L512C, L513E, and A514C; or K77C, I217C,        A424C, V450C, L171C, K191C, F488W, L512C, L513E, A514E, and        G515C;    -   S155C, S290, S190F, and V207L substitutions, and further        comprises one of the following sets of substitutions: L503E, and        I506K; L503E, I506K, and F505W; L503E, I506K, L230F, and L158F;        L503E, I506K, S509F, F505W, L230F, and L158F; L160K, V178T,        L258K, V384T, I431S, and L467Q; F477K, L481Q, V482K, L503Q, and        I506K; L160K, V178T, L258K, V384T, I431S, L467Q, F477K, L481Q,        V482K, L503Q, and I506K; L512C, and L513C; L512C, L513C, L160K,        V178T, L258K, V384T, I431S, and L467Q; L512C, L513C, F477K,        L481Q, V482K, L503Q, and I506K; L512C, L513C, L160K, V178T,        L258K, V384T, I431S, L467Q, F477K, L481Q, V482K, L503Q, and        I506K; F505W; F505W L160K, V178T, L258K, V384T, I431S, and        L467Q; F505W F477K, L481Q, V482K, L503Q, and I506K; F505W L160K,        V178T, L258K, V384T, I431S, L467Q, F477K, L481Q, V482K, L503Q,        and I506K; L512C, L513C, and F505W; L512C, L513C F505W L160K,        V178T, L258K, V384T, I431S, and L467Q; L512C, L513C F505W F477K,        L481Q, V482K, L503Q, and I506K; L512C, L513C F505W L160K, V178T,        L258K, V384T, I431S, L467Q, F477K, L481Q, V482K, L503Q, and        I506K; I506K, S509F, L83F, and V90F; I506K, S509F, L83F, V90F,        L230F, and L158F; I506K, S509F, F505W, L83F, V90F, L230F, V185F,        and T54A; L83F, V90F, L230F, and I395F; I506K, S509F, F505W,        L83F, V90F, L230F, L158F, I395F, V185F, and T54A; L512C, and        L513C; or 486DEF to CPC, wherein the amino acid positions        correspond to the amino acid sequence of a reference F₀        polypeptide set forth as SEQ ID NO: 124.    -   Clause 45. The immunogen of clause 18, wherein the recombinant        RSV F protein is stabilized in the RSV F protein prefusion and        comprises F₂ and F₁ polypeptides comprising the amino acid        sequence set forth as positions 26-109 and 137-513,        respectively, of one of SEQ ID NOs: 338-433, 434-544, 672-682.    -   Clause 46. The immunogen of any one of clauses 1-18, wherein the        recombinant RSV F protein comprises the amino acid substitutions        set forth in one of    -   rows 1-16 of Table 5b (newer interchain disulfides);    -   rows 1-84 of Table 6b (newer cavity filling);    -   rows 1-54 of Table 8b (newer combinations with DSCav-1); or    -   rows 1-13 of Table 8c ((newer cavity filling+replacing exposed        hydrophobic residues); and    -   wherein the amino acid positions correspond to the amino acid        sequence of a reference F₀ polypeptide set forth as SEQ ID NO:        124.    -   Clause 47. The immunogen of of any one of clauses 1-18, wherein        the recombinant RSV F protein is a single chain protein and        comprises an amino acid sequence at least 80% identical to any        one of SEQ ID NOs: 698-828 or 1474-1478.    -   Clause 48. The immunogen of of any one of clauses 1-18, wherein        the recombinant RSV F protein is a single chain protein and        comprises an amino acid sequence at least 80% identical to any        one of SEQ ID NOs: 698-828 or 1474-1478, optionally without the        protein tags or leader sequences listed in the corresponding SEQ        ID NO.    -   Clause 49. The immunogen of of any one of clauses 1-18, wherein        the recombinant RSV F protein comprises a trimerization domain,        further comprising a protease cleavage site between the Foldon        domain and the recombinant RSV F protein.    -   Clause 50. The immunogen of of any one of clauses 1-18, wherein        recombinant RSV F protein comprises the amino acid substitutions        listed in the row of Table 23 corresponding to one of SEQ ID        NOs: 829-1025.    -   Clause 51. The immunogen of of any one of clauses 1-18, wherein        the recombinant RSV F protein comprises the amino acid        substitutions listed in the row of Table 23 corresponding to one        of SEQ ID NOs: 969-1025.    -   Clause 52. The immunogen of of any one of clauses 1-18, wherein        the immunogen comprises one or more of the following amino acid        substitutions: DSCav1-F137C, and R339C; DSCav1-F137C and T337C;        DSCav1-G139C and Q354C; F137C, R339C; F137C, T337C; G139C,        Q354C; L260F; L260W; L260Y; L260R; L188F; L188W; L188Y; L188R;        I57F; I57W; I57R; L252F; L252W; L252R; V192F; V192W; V192R;        S150C and Y458C; A149C and N460C; S146C, and N460C; A149C and        Y458C; V220F; V220W; V220M; T219F; T219M; T219W; T219R; I221F;        I221Y; I221W; Q224D and, L78K; V278F Q279F N277D and, S99K;        Q361F; V402F; T400F; T400W; H486F; H486W; I217F; I217Y; I217W;        F190V; K226L; T58I, and A298M; F190V and K226L; F190V, and T58I,        A298M; K226L, T58I, and A298M; T58I, A298M, F190V and K226L, and        optionally further comprises S155C and S290C substitutions, or        S155C, S290C, S190F and V207L substitution.    -   Clause 53. The immunogen of any one of clauses 1-18, wherein the        immunogen comprises an amino acid sequence at least 80%        identical to the amino acid sequence of one of SEQ ID NOs:        829-1025, optionally without the protein tags or leader        sequences listed in the corresponding SEQ ID NO.    -   Clause 54. The immunogen of any one of clauses 53, wherein the        recombinant RSV F protein comprises a trimerization domain,        further comprising a protease cleavage site between the Foldon        domain and the recombinant RSV F protein.    -   Clause 55. The immunogen of any one of clauses 1-18, wherein        recombinant RSV F protein comprises the amino acid substitutions        listed in the row of Table 24 corresponding to one of SEQ ID        NOs: 901-968.    -   Clause 56 The immunogen of of any one of clauses 1-18, wherein        the immunogen comprises an amino acid sequence at least 80%        identical to the amino acid sequence of one of SEQ ID NOs:        901-968, optionally without the protein tags or leader sequences        listed in the corresponding SEQ ID NO.    -   Clause 57. The immunogen of clause 7, wherein the recombinant        RSV F protein or fragment thereof comprises or consists of an        amino acid sequence at least 80% identical to the following RSV        F₂ and F₁ positions as set forth in any one of SEQ ID NOs:        1-184:    -   (a) 56-97 and 189-211, respectively; (b) 58-97 and 192-242,        respectively; (c) 59-97 and 194-240, respectively; (d) 60-75 and        193-218, respectively; (e) 60-94 and 192-229, respectively; (f)        60-94 and 192-232, respectively; (g) 60-94 and 193-237,        respectively; (h) 60-95 and 192-240, respectively; (i) 60-96 and        192-239, respectively; (j) 60-97 and 192-242, respectively; (k)        60-97 and 194-239, respectively; (1) 61-96 and 192-235,        respectively; (m) 61-96 and 192-240, respectively; (n) 62-69 and        196-209, respectively; or (o) a circular permutation of the F₂        and F₁ positions listed in any one of (a)-(m), wherein the RSV        F₂ and F₁ positions are joined by a heterologous linker.    -   Clause 58. The immunogen of clause 7, wherein the recombinant        RSV F protein or fragment thereof comprises or consists of an        amino acid sequence at least 80% identical to the following RSV        F₂ and F₁ positions as set forth in any one of SEQ ID NOs:        1-184:    -   (a) 46-103 and 147-310, respectively; (b) 46-104 and 146-310,        respectively; (c) 50-96 and 149-306, respectively; (d) 51-103        and 146-307, respectively; (e) 51-103 and 139-307,        respectively; (f) 50-105 and 146-306, respectively; (g) 53-97        and 148 to one of 305-320; (h) a circular permutation of the F₂        and F₁ positions listed in any one of (a)-(g), wherein the RSV        F₂ and F₁ positions are joined by a heterologous linker or are        directly linked.    -   Clause 59. The immunogen of clause 57 or 58, wherein the        recombinant RSV F protein or fragment thereof comprises the        amino acid sequence of any one of the minimal site Ø immunogens        listed in Table 20.    -   Clause 60. The immunogen of clause 57 or 58, wherein the        recombinant RSV F protein or fragment thereof comprises an amino        acid sequence at least 80% identical to the amino acid sequence        of one of SEQ ID NOs: 1027-1218.    -   Clause 61. The immunogen of clause 57 or 58, wherein the        recombinant RSV F protein or fragment thereof comprises an amino        acid sequence at least 80% identical to the amino acid sequence        of one of SEQ ID NOs: 1027-1218, optionally without the protein        tags or leader sequences listed in the corresponding SEQ ID NO.    -   Clause 62. The immunogen any of clauses 58-61, wherein the        recombinant RSV F protein comprises cysteine substitutions at        position 155 and 290, and a F, L, W, Y, H, or M substitution at        position 190, position 207, or positions 190 and 207.    -   Clause 63. The immunogen any of clauses 58-61, wherein the        recombinant RSV F protein comprises S155C and S290C        substitutions; S155C, S290C, and S190F substitutions, or S155C,        S290C, S190F, and V207L substitutions.    -   Clause 64. The immunogen of any of clauses 58-61, wherein the        recombinant RSV F protein or fragment thereof comprises or        consists of the F₁-linker-F₂ sequence or F₂-linker-F₁ sequence        of any one of SEQ ID NOs: 1027-1218.    -   Clause 65. The immunogen of any of clauses 57-64, wherein the        heterologous linker comprises or consists of the amino acid        sequence set forth as any one of SEQ ID NOs: 1443-1455, or a G,        S, GG, GS, SG, GGG, or GSG linker.    -   Clause 66. The immunogen of any of the previous clauses,        comprising a multimer of the recombinant RSV F protein or        fragment thereof.    -   Clause 67. The immunogen of any of the previous clauses, wherein        the recombinant RSV F protein is linked to a scaffold protein.    -   Clause 68. The immunogen of any of clauses 1-56, wherein the F1        polypeptide comprises an RSV α10 helix comprising from RSV        position 492 to one of positions 510-529, and wherein the F1        polypeptide comprises at least two cysteine substitutions that        form a non-natural inter-protomer disulfide bond.    -   Clause 69. The immunogen of 68, wherein positions 512-524 of the        F1 polypeptide comprise the amino acid sequence set forth as        CCHNVNAGKSTTN (residues 512-524 of SEQ ID NO: 844) or        CCHNVNACCSTTN (residues X-Y of SEQ ID NO: 849); or wherein        positions 512-529 of the F1 polypeptide comprise the amino acid        sequence set forth as CCHNVNACCSTTNICCTT (residues 512-529 of        SEQ ID NO: 853).    -   Clause 70. The isolated immunogen of any one of the previous        clauses, wherein the recombinant RSV F protein further comprises        an additional disulfide bond comprising a pair of crosslinked        cysteines at F₁ positions:    -   (a) 486 and 487;    -   (b) 512 and 513;    -   (c) 519 and 520;    -   (d) 526 and 527;    -   (e) 486 and 487, wherein the F₁ polypeptide further comprises a        P inserted between positions 486 and 487;    -   (f) 330 and 493; wherein the F₁ polypeptide further comprises a        C inserted between positions C insertion between positions 329        and 330; or    -   (g) 330 and 493; wherein the F₁ polypeptide further comprises a        C inserted between positions 329 and 330, and a G insertion        between positions 492 and 493;    -   wherein the amino acid positions correspond to the amino acid        sequence of a reference F₀ polypeptide set forth as SEQ ID NO:        124.    -   Clause 71. The immunogen of any of the previous clauses, wherein        the recombinant RSV F protein or fragment thereof or epitope        scaffold protein is linked to a trimerization domain.    -   Clause 72. The immunogen of clause 71, wherein the C-terminus of        the F₁ polypeptide of the recombinant RSV F protein is linked to        the trimerization domain.    -   Clause 73. The immunogen of clause 71 or clause 72, wherein the        trimerization domain is a Foldon domain.    -   Clause 74. The immunogen any of clauses 71-73, further        comprising a protease cleave site between the F₁ polypeptide and        the trimerization domain.    -   Clause 75. The immunogen of clause 74, further comprising a        transmembrane domain between the protease cleave site and the        trimerization domain.    -   Clause 76. The isolated immunogen of clause 75, wherein the RSV        F protein is stabilized in the F protein prefusion conformation        by    -   (a) the disulfide bond, wherein the F₂ polypeptide and the F₁        polypeptide linked to the Foldon domain comprise the amino acid        sequence set forth as positions 26-109 and 137-544,        respectively, of any one of SEQ ID NOs: 185, 189, 190, 201, 202,        205, 207, 209, 211, 212, 213, 244, 245, 247, 257, 258, 259, 260,        261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273,        274, 275, 277, 278, 279, 280, 281, 282, 284, 302, 303, 243, 246,        276, 283, 285, 296, 297, 298, or 299;    -   (b) the cavity-filling amino acid substitution, wherein the F₂        polypeptide and the F₁ polypeptide linked to the Foldon domain        comprise the amino acid sequence set forth as positions 26-109        and 137-544, respectively, of any one of SEQ ID NOs: 191, 193,        196, 197, 248, 192, 195, or 194;    -   (c) the repacking amino acid substitution, wherein the F₂        polypeptide and the F₁ polypeptide linked to the Foldon domain        comprise the amino acid sequence set forth as positions 26-109        and 137-544, respectively, of any one of SEQ ID NOs: 249, 250,        251, 252, 253, 254, 255, 256, 288, 289, 290, 291, 292, 293, 294,        295, 296, 297, 326, 327, 328, 329, 330, 331, 332, 333, 334, 335,        336, or 337; or    -   (d) the N-linked glycosylation site, wherein the F₂ polypeptide        and the F₁ polypeptide linked to the Foldon domain comprise the        amino acid sequence set forth as positions 26-109 and 137-544,        respectively, of any one of SEQ ID NOs selected from the group        consisting of SEQ ID NOs: 198, 199, 200, 203, 204, 214, 215,        216, or 217;    -   (e) the disulfide bond and the cavity filling substitution,        wherein the F₂ polypeptide and the F₁ polypeptide linked to the        Foldon domain comprise the amino acid sequence set forth as        positions 26-109 and 137-544, respectively, of any one of SEQ ID        NOs selected from the group consisting of SEQ ID NOs: 371, 372,        373, 374, 375, 376; and    -   wherein the amino acid positions correspond to the amino acid        sequence of a reference F₀ polypeptide set forth as SEQ ID NO:        124.    -   Clause 77. The isolated immunogen of clause 75, wherein the F₂        polypeptide and the F₁ polypeptide linked to the Foldon domain        comprise the amino acid sequence set forth as positions 26-109        and 137-548, respectively, of any one of SEQ ID NO: 552; 553;        554; 555; 556; 557; 558; 559; 560; 561; 562; 563; 564; 565; 566;        567; 568; 569; 570; 571; 572; 573; 574; 575; 576; 577; 578; 579;        580; 581; 582; 583; 584; 585; 586; 587; 588; 589; 590; 591; 592;        593; and 601; 683; 684; 685; 686; 687; 688; 689; 690; 691; 692;        or 693.    -   wherein the amino acid positions correspond to the amino acid        sequence of a reference F₀ polypeptide set forth as SEQ ID NO:        124.    -   Clause 78. The immunogen of any one of the previous clauses,        wherein the recombinant RSV F protein or fragment thereof or        epitope scaffold protein is linked to a protein nanoparticle        subunit.    -   Clause 79. The immunogen of clause 78, wherein the C-terminus of        the recombinant RSV F protein or fragment thereof or epitope        scaffold protein is linked to the protein nanoparticle subunit.    -   Clause 80. The immunogen of clause 78 or clause 79, wherein the        protein nanoparticle subunit is a ferritin, encapsulin, Sulfur        Oxygenase Reductase (SOR), lumazine synthase, or pyruvate        dehydrogenase nanoparticle subunit.    -   Clause 81. The immunogen of clause 78, wherein:    -   the ferritin nanoparticle subunit comprises an amino acid        sequence having at least 80% sequence identity to residues        517-679 of SEQ ID NO: 350, and optionally includes a C31S, C31A        or C31V substitution in the ferritin polypeptide;    -   the SOR subunit comprises an amino acid sequence having at least        80% sequence identity to residues 516-825 of SEQ ID NO: 344 or        SEQ ID NO: 345;    -   the lumazine synthase subunit comprises an amino acid sequence        having at least 80% sequence identity to residues 517-670 of SEQ        ID NO: 346 or SEQ ID NO: 348, or residues 517-669 of SEQ ID NO:        347; or    -   the pyruvate dehydrogenase synthase subunit an amino acid        sequence having at least 80% sequence identity to residues        516-757 of SEQ ID NO: 349.    -   Clause 82. The immunogen of clause 78, comprising a single chain        RSV F protein linked to a ferritin subunit comprising an amino        acid sequence at least 80% identical one of SEQ ID NOs: 827-828        or 1429-1442    -   Clause 83. The immunogen of clause 78, wherein the recombinant        RSV F protein or fragment thereof is linked to a nanoparticle        subunit, and comprises the amino acid sequence of any one of the        Minimal site Ø immunogens linked to a protein nanoparticle as        listed in Table 21.    -   Clause 84. The immunogen of clause 78, wherein the recombinant        RSV F protein or fragment thereof is linked to a nanoparticle        subunit, comprises an amino acid sequence at least 80% identical        to the amino acid sequence of one of SEQ ID NOs: 1219-1428.    -   Clause 85. The immunogen of clause 78, wherein the recombinant        RSV F protein, or fragment thereof is linked to a nanoparticle        subunit and comprises an amino acid sequence at least 80%        identical to the amino acid sequence of one of SEQ ID NOs:        1219-1428, optionally without the protein tags or leader        sequences listed in the corresponding SEQ ID NO.    -   Clause 86. The immunogen of any of the previous clauses, wherein        the recombinant RSV F protein forms a trimer in phosphate        buffered saline at physiological pH at room temperature.    -   Clause 87. The immunogen any of the previous clauses, wherein        the immunogen forms a homogeneous population of immunogens when        incubated in aqueous solution, wherein at least 70%, at least        80%, at least 90%, and/or at least 95% of the immunogens        incubated in the solution specifically bind to the        prefusion-specific antibody after:    -   (a) incubation for one hour in 350 mM NaCl pH 7.0, at 50° C.;    -   (b) incubation for one hour in 350 mM NaCl pH 3.5, at 25° C.;    -   (c) incubation for one hour in 350 mM NaCl pH 10, at 25° C.;    -   (d) incubation for one hour in 10 mM osmolarity, pH 7.0, at 25°        C.;    -   (e) incubation for one hour in 3000 mM osmolarity, pH 7.0, at        25° C.; or    -   (f) ten freeze-thaw cycles in 350 mM NaCl pH 7.0; or    -   (g) a combination of two or more of (a)-(f); wherein    -   the immunogen is incubated in the solution in the absence of the        prefusion-specific antibody.    -   Clause 88. The immunogen any of the previous clauses, wherein:    -   (a) the recombinant RSV F protein or fragment thereof does not        include a disulfide bond between RSV F positions 481 and 489, or        between RSV F positions 509 and 510;    -   (b) the recombinant RSV F protein or fragment thereof does not        include a cysteine residue at RSV F positions 481, 489, 509, 510        or a combination thereof;    -   (c) a combination of (a) and (b).    -   Clause 89. The isolated immunogen of any one of clauses 1-70,        wherein the C-terminus of the F₁ polypeptide, is linked to a        transmembrane domain.    -   Clause 90. The isolated immunogen of clause 89, wherein        transmembrane domain is a RSV F transmembrane domain.    -   Clause 91. The isolated immunogen of clause 89 or 90, wherein        the C-terminus of the transmembrane domain is linked to a RSV F        cytosolic domain.    -   Clause 92. The isolated immunogen of any one of the previous        clauses, wherein the immunogen is not stabilized in the        prefusion conformation by non-specific crosslinking.    -   Clause 93. A virus-like particle comprising the immunogen of any        one of clauses 1-70.    -   Clause 94. A protein nanoparticle comprising the immunogen of        any one of clauses 1-85.    -   Clause 95. The protein nanoparticle of clause 94, wherein the        protein nanoparticle is a ferritin nanoparticle, an encapsulin        nanoparticle, a Sulfur Oxygenase Reductase (SOR) nanoparticle, a        lumazine synthase nanoparticle or a pyruvate dehydrogenase        nanoparticle.    -   Clause 96. The immunogen, of any one of clauses 1-92, wherein a        Fab of monoclonal antibody D25 or AM22 specifically binds to the        immunogen, the virus-like particle, or the protein nanoparticle        with a K_(d) of 1 μM or less.    -   Clause 97. The isolated immunogen of any one of clauses 1-85,        wherein the immunogen comprises a D25 epitope comprising a        three-dimensional structure that in the absence of monoclonal        antibody D25 can be structurally superimposed onto the        three-dimensional structure of a D25 epitope comprising residues        62-69 and 196-209 of SEQ ID NO: 370 in complex with monoclonal        antibody D25 as defined by the atomic coordinates set forth in        Table 1 with a root mean square deviation (RMSD) of their        coordinates of less than 2.0 Å/residue, wherein the RMSD is        measured over the polypeptide backbone atoms N, Cα, C, O, for at        least three consecutive amino acids.    -   Clause 98. A nucleic acid molecule encoding the isolated        immunogen of any one of clauses 1-92.    -   Clause 99. The nucleic acid molecule of clause 98, wherein the        nucleic acid molecule encodes a precursor protein of the        immunogen.    -   Clause 100. The nucleic acid molecule of clause 99, wherein the        precursor protein comprises, from N- to C-terminus, a signal        peptide, the F₂ polypeptide, a Pep27 polypeptide, and the F₁        polypeptide.    -   Clause 101. The nucleic acid molecule of clause 100, wherein the        Pep27 polypeptide comprises the amino acid sequence set forth as        positions 110-136 of any one SEQ ID NOs: 1-184 or 370, wherein        the amino acid positions correspond to the amino acid sequence        of a reference F₀ polypeptide set forth as SEQ ID NO: 124.    -   Clause 102. The nucleic acid molecule of clause 101, wherein the        signal peptide comprises the amino acid sequence set forth as        positions 1-25 of any one SEQ ID NOs: 1-184 or 370, wherein the        amino acid positions correspond to the amino acid sequence of a        reference F₀ polypeptide set forth as SEQ ID NO: 124.    -   Clause 103. The nucleic acid molecule of any one of clauses        99-102, codon optimized for expression in a human or a bovine        cell.    -   Clause 104. The nucleic acid molecule of any one of clauses        99-103, operably linked to a promoter.    -   Clause 105. A vector comprising the nucleic acid molecule of        clause 104.    -   Clause 106. The vector of clause 105, wherein the vector is a        viral vector.    -   Clause 107. The viral vector of clause 106, wherein the viral        vector is a bovine parainfluenza virus vector, a human        parainfluenza virus vector, a Newcastle disease virus vector, a        Sendai virus vector, a measles virus vector, an attenuated RSV        vector, a paramyxovirus vector, an adenovirus vector, an        alphavirus vector, a Venezuelan equine encephalitis vector, a        Semliki Forest virus vector, a Sindbis virus vector, an        adeno-associated virus vector, a poxvirus vector, a rhabdovirus        vector, a vesicular stomatitis virus vector, a picornovirus        vector, or a herpesvirus vector.    -   Clause 108. The vector of clause 106, wherein the vector is a        bacterial vector.    -   Clause 109. The bacterial vector of clause 108, wherein the        bacterial vector is a mycobacterial vector, a salmonella vector,        a shigella vector, a Listeria monocytogenes vector, or a        lactobacillus vector.    -   Clause 110. The nucleic acid molecule or vector of any one of        clauses 98-109, comprising the nucleotide sequence set forth as        SEQ ID NO: 383, SEQ ID NO: 384, SEQ ID NO: 385, or SEQ ID NO:        386.    -   Clause 111. An isolated host cell comprising the vector of any        one of clauses 105-110.    -   Clause 112. An immunogenic composition comprising an effective        amount of the immunogen, virus-like particle, protein        nanoparticle, nucleic acid molecule, or vector of any one of        clauses 1-110; and a pharmaceutically acceptable carrier.    -   Clause 113. The immunogenic composition of clause 112, further        comprising an adjuvant.    -   Clause 114. The immunogenic composition of clause 113, wherein        the adjuvant is alum, an oil-in water composition, MF59, AS01,        AS03, AS04, MPL, QS21, a CpG oligonucleotide, a TLR7 agonist, a        TLR4 agonist, or a combination of two or more thereof.    -   Clause 115. The immunogenic composition of clause 113, wherein        the adjuvant promotes a Th1 immune response.    -   Clause 116. The immunogenic composition of any of clauses 112,        further comprising a RSV F prefusion specific antibody that        specifically binds the immunogen.    -   Clause 117. The immunogenic composition of any one of clauses        112, comprising a mixture of recombinant RSV F proteins or        fragments thereof based on RSV F protein subtype A and B.    -   Clause 118. The immunogenic composition of clause 117, wherein    -   the human subtype A RSV F protein comprises S155C, S290C, and        S190F substitutions, and the human subtype B RSV F protein        comprises S155C, S290C, and S190F substitutions; or    -   the human subtype A RSV F protein comprises S155C, S290C, S190F,        and V207L substitutions, and the human subtype B RSV F protein        comprises S155C, S290C, S190F, and V207L substitutions.    -   Clause 119. A method for generating an immune response to RSV F        in a subject, comprising administering to the subject an        effective amount of the immunogenic composition of any one of        clauses 112-118 to generate the immune response.    -   Clause 120. The method of clause 119, wherein the immune        response comprises a Th1 immune response.    -   Clause 121. A method for treating or preventing a RSV infection        in a subject, comprising administering to the subject a        therapeutically effective amount of the immunogenic composition        of any one of clauses 112-120, thereby treating or preventing        RSV infection in the subject.    -   Clause 122. The method of any one of clauses 119-121, comprising        a prime-boost administration of the immunogenic composition.    -   Clause 123. The method of clause 122, wherein the prime and        boost comprise administration of a mixture of recombinant RSV F        proteins or fragments thereof or nucleic acid molecules or        protein nanoparticles based on RSV F protein subtype A and B.    -   Clause 124. A method for detecting or isolating an RSV F binding        antibody in a subject, comprising: providing an effective amount        of the immunogen, virus-like particle, protein nanoparticle,        nucleic acid molecule, or vector of any one of clauses 1-110;    -   contacting a biological sample from the subject with the        recombinant RSV F protein or the protein nanoparticle under        conditions sufficient to form an immune complex between the        recombinant RSV F protein or the protein nanoparticle and the        RSV F binding antibody; and detecting the immune complex,        thereby detecting or isolating the RSV F binding antibody in the        subject.    -   Clause 125. The method of any one of clauses 119-124, wherein        the subject is at risk of or has an RSV infection.    -   Clause 126. The method of clause 125, wherein the RSV infection        is a human RSV subtype A, human RSV subtype B, or bovine RSV        infection.    -   Clause 127. The method of any one of clauses 119-126, wherein        the subject is a human or a veterinary subject.    -   Clause 129. A kit comprising the immunogen, virus-like particle,        protein nanoparticle, nucleic acid molecule, or vector of any        one of clauses 1-110; and instructions for using the kit.        As used herein, reference to:    -   “any one of SEQ ID NOs: 1-184” refers to “SEQ ID NO: 1, SEQ ID        NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6,        SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID        NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO:        15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19,        SEQ ID NO: 20, SEQ ID NO: 21, SEQ ID NO: 22, SEQ ID NO: 23, SEQ        ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID        NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO:        32, SEQ ID NO: 33, SEQ ID NO: 34, SEQ ID NO: 35, SEQ ID NO: 36,        SEQ ID NO: 37, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 40, SEQ        ID NO: 41, SEQ ID NO: 42, SEQ ID NO: 43, SEQ ID NO: 44, SEQ ID        NO: 45, SEQ ID NO: 46, SEQ ID NO: 47, SEQ ID NO: 48, SEQ ID NO:        49, SEQ ID NO: 50, SEQ ID NO: 51, SEQ ID NO: 52, SEQ ID NO: 53,        SEQ ID NO: 54, SEQ ID NO: 55, SEQ ID NO: 56, SEQ ID NO: 57, SEQ        ID NO: 58, SEQ ID NO: 59, SEQ ID NO: 60, SEQ ID NO: 61, SEQ ID        NO: 62, SEQ ID NO: 63, SEQ ID NO: 64, SEQ ID NO: 65, SEQ ID NO:        66, SEQ ID NO: 67, SEQ ID NO: 68, SEQ ID NO: 69, SEQ ID NO: 70,        SEQ ID NO: 71, SEQ ID NO: 72, SEQ ID NO: 73, SEQ ID NO: 74, SEQ        ID NO: 75, SEQ ID NO: 76, SEQ ID NO: 77, SEQ ID NO: 78, SEQ ID        NO: 79, SEQ ID NO: 80, SEQ ID NO: 81, SEQ ID NO: 82, SEQ ID NO:        83, SEQ ID NO: 84, SEQ ID NO: 85, SEQ ID NO: 86, SEQ ID NO: 87,        SEQ ID NO: 88, SEQ ID NO: 89, SEQ ID NO: 90, SEQ ID NO: 91, SEQ        ID NO: 92, SEQ ID NO: 93, SEQ ID NO: 94, SEQ ID NO: 95, SEQ ID        NO: 96, SEQ ID NO: 97, SEQ ID NO: 98, SEQ ID NO: 99, SEQ ID NO:        100, SEQ ID NO: 101, SEQ ID NO: 102, SEQ ID NO: 103, SEQ ID NO:        104, SEQ ID NO: 105, SEQ ID NO: 106, SEQ ID NO: 107, SEQ ID NO:        108, SEQ ID NO: 109, SEQ ID NO: 110, SEQ ID NO: 111, SEQ ID NO:        112, SEQ ID NO: 113, SEQ ID NO: 114, SEQ ID NO: 115, SEQ ID NO:        116, SEQ ID NO: 117, SEQ ID NO: 118, SEQ ID NO: 119, SEQ ID NO:        120, SEQ ID NO: 121, SEQ ID NO: 122, SEQ ID NO: 123, SEQ ID NO:        124, SEQ ID NO: 125, SEQ ID NO: 126, SEQ ID NO: 127, SEQ ID NO:        128, SEQ ID NO: 129, SEQ ID NO: 130, SEQ ID NO: 131, SEQ ID NO:        132, SEQ ID NO: 133, SEQ ID NO: 134, SEQ ID NO: 135, SEQ ID NO:        136, SEQ ID NO: 137, SEQ ID NO: 138, SEQ ID NO: 139, SEQ ID NO:        140, SEQ ID NO: 141, SEQ ID NO: 142, SEQ ID NO: 143, SEQ ID NO:        144, SEQ ID NO: 145, SEQ ID NO: 146, SEQ ID NO: 147, SEQ ID NO:        148, SEQ ID NO: 149, SEQ ID NO: 150, SEQ ID NO: 151, SEQ ID NO:        152, SEQ ID NO: 153, SEQ ID NO: 154, SEQ ID NO: 155, SEQ ID NO:        156, SEQ ID NO: 157, SEQ ID NO: 158, SEQ ID NO: 159, SEQ ID NO:        160, SEQ ID NO: 161, SEQ ID NO: 162, SEQ ID NO: 163, SEQ ID NO:        164, SEQ ID NO: 165, SEQ ID NO: 166, SEQ ID NO: 167, SEQ ID NO:        168, SEQ ID NO: 169, SEQ ID NO: 170, SEQ ID NO: 171, SEQ ID NO:        172, SEQ ID NO: 173, SEQ ID NO: 174, SEQ ID NO: 175, SEQ ID NO:        176, SEQ ID NO: 177, SEQ ID NO: 178, SEQ ID NO: 179, SEQ ID NO:        180, SEQ ID NO: 181, SEQ ID NO: 182, SEQ ID NO: 183, or SEQ ID        NO: 184”    -   “SEQ ID NOs: 698-828” refers to “any one of “SEQ ID NO: 699, SEQ        ID NO: 700, SEQ ID NO: 701, SEQ ID NO: 702, SEQ ID NO: 703, SEQ        ID NO: 704, SEQ ID NO: 705, SEQ ID NO: 706, SEQ ID NO: 707, SEQ        ID NO: 708, SEQ ID NO: 709, SEQ ID NO: 710, SEQ ID NO: 711, SEQ        ID NO: 712, SEQ ID NO: 713, SEQ ID NO: 714, SEQ ID NO: 715, SEQ        ID NO: 716, SEQ ID NO: 717, SEQ ID NO: 718, SEQ ID NO: 719, SEQ        ID NO: 720, SEQ ID NO: 721, SEQ ID NO: 722, SEQ ID NO: 723, SEQ        ID NO: 724, SEQ ID NO: 725, SEQ ID NO: 726, SEQ ID NO: 727, SEQ        ID NO: 728, SEQ ID NO: 729, SEQ ID NO: 730, SEQ ID NO: 731, SEQ        ID NO: 732, SEQ ID NO: 733, SEQ ID NO: 734, SEQ ID NO: 735, SEQ        ID NO: 736, SEQ ID NO: 737, SEQ ID NO: 738, SEQ ID NO: 739, SEQ        ID NO: 740, SEQ ID NO: 741, SEQ ID NO: 742, SEQ ID NO: 743, SEQ        ID NO: 744, SEQ ID NO: 745, SEQ ID NO: 746, SEQ ID NO: 747, SEQ        ID NO: 748, SEQ ID NO: 749, SEQ ID NO: 750, SEQ ID NO: 751, SEQ        ID NO: 752, SEQ ID NO: 753, SEQ ID NO: 754, SEQ ID NO: 755, SEQ        ID NO: 756, SEQ ID NO: 757, SEQ ID NO: 758, SEQ ID NO: 759, SEQ        ID NO: 760, SEQ ID NO: 761, SEQ ID NO: 762, SEQ ID NO: 763, SEQ        ID NO: 764, SEQ ID NO: 765, SEQ ID NO: 766, SEQ ID NO: 767, SEQ        ID NO: 768, SEQ ID NO: 769, SEQ ID NO: 770, SEQ ID NO: 771, SEQ        ID NO: 772, SEQ ID NO: 773, SEQ ID NO: 774, SEQ ID NO: 775, SEQ        ID NO: 776, SEQ ID NO: 777, SEQ ID NO: 778, SEQ ID NO: 779, SEQ        ID NO: 780, SEQ ID NO: 781, SEQ ID NO: 782, SEQ ID NO: 783, SEQ        ID NO: 784, SEQ ID NO: 785, SEQ ID NO: 786, SEQ ID NO: 787, SEQ        ID NO: 788, SEQ ID NO: 789, SEQ ID NO: 790, SEQ ID NO: 791, SEQ        ID NO: 792, SEQ ID NO: 793, SEQ ID NO: 794, SEQ ID NO: 795, SEQ        ID NO: 796, SEQ ID NO: 797, SEQ ID NO: 798, SEQ ID NO: 799, SEQ        ID NO: 800, SEQ ID NO: 801, SEQ ID NO: 802, SEQ ID NO: 803, SEQ        ID NO: 804, SEQ ID NO: 805, SEQ ID NO: 806, SEQ ID NO: 807, SEQ        ID NO: 808, SEQ ID NO: 809, SEQ ID NO: 810, SEQ ID NO: 811, SEQ        ID NO: 812, SEQ ID NO: 813, SEQ ID NO: 814, SEQ ID NO: 815, SEQ        ID NO: 816, SEQ ID NO: 817, SEQ ID NO: 818, SEQ ID NO: 819, SEQ        ID NO: 820, SEQ ID NO: 821, SEQ ID NO: 822, SEQ ID NO: 823, SEQ        ID NO: 824, SEQ ID NO: 825, SEQ ID NO: 826, SEQ ID NO: 827, or        SEQ ID NO: 828.”    -   “SEQ ID NOs: 1474-1478” refers to “any one of SEQ ID NO: 1474,        SEQ ID NO: 1475, SEQ ID NO: 1476, SEQ ID NO: 1477, or SEQ ID NO:        1478.”    -   “SEQ ID NOs: 829-1025” refers to “any one of SEQ ID NO: 829, SEQ        ID NO: 830, SEQ ID NO: 831, SEQ ID NO: 832, SEQ ID NO: 833, SEQ        ID NO: 834, SEQ ID NO: 835, SEQ ID NO: 836, SEQ ID NO: 837, SEQ        ID NO: 838, SEQ ID NO: 839, SEQ ID NO: 840, SEQ ID NO: 841, SEQ        ID NO: 842, SEQ ID NO: 843, SEQ ID NO: 844, SEQ ID NO: 845, SEQ        ID NO: 846, SEQ ID NO: 847, SEQ ID NO: 848, SEQ ID NO: 849, SEQ        ID NO: 850, SEQ ID NO: 851, SEQ ID NO: 852, SEQ ID NO: 853, SEQ        ID NO: 854, SEQ ID NO: 855, SEQ ID NO: 856, SEQ ID NO: 857, SEQ        ID NO: 858, SEQ ID NO: 859, SEQ ID NO: 860, SEQ ID NO: 861, SEQ        ID NO: 862, SEQ ID NO: 863, SEQ ID NO: 864, SEQ ID NO: 865, SEQ        ID NO: 866, SEQ ID NO: 867, SEQ ID NO: 868, SEQ ID NO: 869, SEQ        ID NO: 870, SEQ ID NO: 871, SEQ ID NO: 872, SEQ ID NO: 873, SEQ        ID NO: 874, SEQ ID NO: 875, SEQ ID NO: 876, SEQ ID NO: 877, SEQ        ID NO: 878, SEQ ID NO: 879, SEQ ID NO: 880, SEQ ID NO: 881, SEQ        ID NO: 882, SEQ ID NO: 883, SEQ ID NO: 884, SEQ ID NO: 885, SEQ        ID NO: 886, SEQ ID NO: 887, SEQ ID NO: 888, SEQ ID NO: 889, SEQ        ID NO: 890, SEQ ID NO: 891, SEQ ID NO: 892, SEQ ID NO: 893, SEQ        ID NO: 894, SEQ ID NO: 895, SEQ ID NO: 896, SEQ ID NO: 897, SEQ        ID NO: 898, SEQ ID NO: 899, SEQ ID NO: 900, SEQ ID NO: 901, SEQ        ID NO: 902, SEQ ID NO: 903, SEQ ID NO: 904, SEQ ID NO: 905, SEQ        ID NO: 906, SEQ ID NO: 907, SEQ ID NO: 908, SEQ ID NO: 909, SEQ        ID NO: 910, SEQ ID NO: 911, SEQ ID NO: 912, SEQ ID NO: 913, SEQ        ID NO: 914, SEQ ID NO: 915, SEQ ID NO: 916, SEQ ID NO: 917, SEQ        ID NO: 918, SEQ ID NO: 919, SEQ ID NO: 920, SEQ ID NO: 921, SEQ        ID NO: 922, SEQ ID NO: 923, SEQ ID NO: 924, SEQ ID NO: 925, SEQ        ID NO: 926, SEQ ID NO: 927, SEQ ID NO: 928, SEQ ID NO: 929, SEQ        ID NO: 930, SEQ ID NO: 931, SEQ ID NO: 932, SEQ ID NO: 933, SEQ        ID NO: 934, SEQ ID NO: 935, SEQ ID NO: 936, SEQ ID NO: 937, SEQ        ID NO: 938, SEQ ID NO: 939, SEQ ID NO: 940, SEQ ID NO: 941, SEQ        ID NO: 942, SEQ ID NO: 943, SEQ ID NO: 944, SEQ ID NO: 945, SEQ        ID NO: 946, SEQ ID NO: 947, SEQ ID NO: 948, SEQ ID NO: 949, SEQ        ID NO: 950, SEQ ID NO: 951, SEQ ID NO: 952, SEQ ID NO: 953, SEQ        ID NO: 954, SEQ ID NO: 955, SEQ ID NO: 956, SEQ ID NO: 957, SEQ        ID NO: 958, SEQ ID NO: 959, SEQ ID NO: 960, SEQ ID NO: 961, SEQ        ID NO: 962, SEQ ID NO: 963, SEQ ID NO: 964, SEQ ID NO: 965, SEQ        ID NO: 966, SEQ ID NO: 967, SEQ ID NO: 968, SEQ ID NO: 969, SEQ        ID NO: 970, SEQ ID NO: 971, SEQ ID NO: 972, SEQ ID NO: 973, SEQ        ID NO: 974, SEQ ID NO: 975, SEQ ID NO: 976, SEQ ID NO: 977, SEQ        ID NO: 978, SEQ ID NO: 979, SEQ ID NO: 980, SEQ ID NO: 981, SEQ        ID NO: 982, SEQ ID NO: 983, SEQ ID NO: 984, SEQ ID NO: 985, SEQ        ID NO: 986, SEQ ID NO: 987, SEQ ID NO: 988, SEQ ID NO: 989, SEQ        ID NO: 990, SEQ ID NO: 991, SEQ ID NO: 992, SEQ ID NO: 993, SEQ        ID NO: 994, SEQ ID NO: 995, SEQ ID NO: 996, SEQ ID NO: 997, SEQ        ID NO: 998, SEQ ID NO: 999, SEQ ID NO: 1000, SEQ ID NO: 1001,        SEQ ID NO: 1002, SEQ ID NO: 1003, SEQ ID NO: 1004, SEQ ID NO:        1005, SEQ ID NO: 1006, SEQ ID NO: 1007, SEQ ID NO: 1008, SEQ ID        NO: 1009, SEQ ID NO: 1010, SEQ ID NO: 1011, SEQ ID NO: 1012, SEQ        ID NO: 1013, SEQ ID NO: 1014, SEQ ID NO: 1015, SEQ ID NO: 1016,        SEQ ID NO: 1017, SEQ ID NO: 1018, SEQ ID NO: 1019, SEQ ID NO:        1020, SEQ ID NO: 1021, SEQ ID NO: 1022, SEQ ID NO: 1023, SEQ ID        NO: 1024, or SEQ ID NO: 1025.”    -   “SEQ ID NOs: 969-1025” refers to “any one of SEQ ID NO: 969, SEQ        ID NO: 970, SEQ ID NO: 971, SEQ ID NO: 972, SEQ ID NO: 973, SEQ        ID NO: 974, SEQ ID NO: 975, SEQ ID NO: 976, SEQ ID NO: 977, SEQ        ID NO: 978, SEQ ID NO: 979, SEQ ID NO: 980, SEQ ID NO: 981, SEQ        ID NO: 982, SEQ ID NO: 983, SEQ ID NO: 984, SEQ ID NO: 985, SEQ        ID NO: 986, SEQ ID NO: 987, SEQ ID NO: 988, SEQ ID NO: 989, SEQ        ID NO: 990, SEQ ID NO: 991, SEQ ID NO: 992, SEQ ID NO: 993, SEQ        ID NO: 994, SEQ ID NO: 995, SEQ ID NO: 996, SEQ ID NO: 997, SEQ        ID NO: 998, SEQ ID NO: 999, SEQ ID NO: 1000, SEQ ID NO: 1001,        SEQ ID NO: 1002, SEQ ID NO: 1003, SEQ ID NO: 1004, SEQ ID NO:        1005, SEQ ID NO: 1006, SEQ ID NO: 1007, SEQ ID NO: 1008, SEQ ID        NO: 1009, SEQ ID NO: 1010, SEQ ID NO: 1011, SEQ ID NO: 1012, SEQ        ID NO: 1013, SEQ ID NO: 1014, SEQ ID NO: 1015, SEQ ID NO: 1016,        SEQ ID NO: 1017, SEQ ID NO: 1018, SEQ ID NO: 1019, SEQ ID NO:        1020, SEQ ID NO: 1021, SEQ ID NO: 1022, SEQ ID NO: 1023, SEQ ID        NO: 1024, or SEQ ID NO: 1025.”    -   “SEQ ID NOs: 901-968” refers to “any one of SEQ ID NO: 901, SEQ        ID NO: 902, SEQ ID NO: 903, SEQ ID NO: 904, SEQ ID NO: 905, SEQ        ID NO: 906, SEQ ID NO: 907, SEQ ID NO: 908, SEQ ID NO: 909, SEQ        ID NO: 910, SEQ ID NO: 911, SEQ ID NO: 912, SEQ ID NO: 913, SEQ        ID NO: 914, SEQ ID NO: 915, SEQ ID NO: 916, SEQ ID NO: 917, SEQ        ID NO: 918, SEQ ID NO: 919, SEQ ID NO: 920, SEQ ID NO: 921, SEQ        ID NO: 922, SEQ ID NO: 923, SEQ ID NO: 924, SEQ ID NO: 925, SEQ        ID NO: 926, SEQ ID NO: 927, SEQ ID NO: 928, SEQ ID NO: 929, SEQ        ID NO: 930, SEQ ID NO: 931, SEQ ID NO: 932, SEQ ID NO: 933, SEQ        ID NO: 934, SEQ ID NO: 935, SEQ ID NO: 936, SEQ ID NO: 937, SEQ        ID NO: 938, SEQ ID NO: 939, SEQ ID NO: 940, SEQ ID NO: 941, SEQ        ID NO: 942, SEQ ID NO: 943, SEQ ID NO: 944, SEQ ID NO: 945, SEQ        ID NO: 946, SEQ ID NO: 947, SEQ ID NO: 948, SEQ ID NO: 949, SEQ        ID NO: 950, SEQ ID NO: 951, SEQ ID NO: 952, SEQ ID NO: 953, SEQ        ID NO: 954, SEQ ID NO: 955, SEQ ID NO: 956, SEQ ID NO: 957, SEQ        ID NO: 958, SEQ ID NO: 959, SEQ ID NO: 960, SEQ ID NO: 961, SEQ        ID NO: 962, SEQ ID NO: 963, SEQ ID NO: 964, SEQ ID NO: 965, SEQ        ID NO: 966, SEQ ID NO: 967, or SEQ ID NO: 968.”    -   “SEQ ID NOs: 1027-1218” refers to “any one of SEQ ID NO: 1027,        SEQ ID NO: 1028, SEQ ID NO: 1029, SEQ ID NO: 1030, SEQ ID NO:        1031, SEQ ID NO: 1032, SEQ ID NO: 1033, SEQ ID NO: 1034, SEQ ID        NO: 1035, SEQ ID NO: 1036, SEQ ID NO: 1037, SEQ ID NO: 1038, SEQ        ID NO: 1039, SEQ ID NO: 1040, SEQ ID NO: 1041, SEQ ID NO: 1042,        SEQ ID NO: 1043, SEQ ID NO: 1044, SEQ ID NO: 1045, SEQ ID NO:        1046, SEQ ID NO: 1047, SEQ ID NO: 1048, SEQ ID NO: 1049, SEQ ID        NO: 1050, SEQ ID NO: 1051, SEQ ID NO: 1052, SEQ ID NO: 1053, SEQ        ID NO: 1054, SEQ ID NO: 1055, SEQ ID NO: 1056, SEQ ID NO: 1057,        SEQ ID NO: 1058, SEQ ID NO: 1059, SEQ ID NO: 1060, SEQ ID NO:        1061, SEQ ID NO: 1062, SEQ ID NO: 1063, SEQ ID NO: 1064, SEQ ID        NO: 1065, SEQ ID NO: 1066, SEQ ID NO: 1067, SEQ ID NO: 1068, SEQ        ID NO: 1069, SEQ ID NO: 1070, SEQ ID NO: 1071, SEQ ID NO: 1072,        SEQ ID NO: 1073, SEQ ID NO: 1074, SEQ ID NO: 1075, SEQ ID NO:        1076, SEQ ID NO: 1077, SEQ ID NO: 1078, SEQ ID NO: 1079, SEQ ID        NO: 1080, SEQ ID NO: 1081, SEQ ID NO: 1082, SEQ ID NO: 1083, SEQ        ID NO: 1084, SEQ ID NO: 1085, SEQ ID NO: 1086, SEQ ID NO: 1087,        SEQ ID NO: 1088, SEQ ID NO: 1099, SEQ ID NO: 1100, SEQ ID NO:        1101, SEQ ID NO: 1102, SEQ ID NO: 1103, SEQ ID NO: 1104, SEQ ID        NO: 1105, SEQ ID NO: 1106, SEQ ID NO: 1107, SEQ ID NO: 1108, SEQ        ID NO: 1109, SEQ ID NO: 1110, SEQ ID NO: 1111, SEQ ID NO: 1112,        SEQ ID NO: 1113, SEQ ID NO: 1114, SEQ ID NO: 1115, SEQ ID NO:        1116, SEQ ID NO: 1117, SEQ ID NO: 1118, SEQ ID NO: 1119, SEQ ID        NO: 1120, SEQ ID NO: 1121, SEQ ID NO: 1122, SEQ ID NO: 1123, SEQ        ID NO: 1124, SEQ ID NO: 1125, SEQ ID NO: 1126, SEQ ID NO: 1127,        SEQ ID NO: 1128, SEQ ID NO: 1129, SEQ ID NO: 1130, SEQ ID NO:        1131, SEQ ID NO: 1132, SEQ ID NO: 1133, SEQ ID NO: 1134, SEQ ID        NO: 1135, SEQ ID NO: 1136, SEQ ID NO: 1137, SEQ ID NO: 1138, SEQ        ID NO: 1139, SEQ ID NO: 1140, SEQ ID NO: 1141, SEQ ID NO: 1142,        SEQ ID NO: 1143, SEQ ID NO: 1144, SEQ ID NO: 1145, SEQ ID NO:        1146, SEQ ID NO: 1147, SEQ ID NO: 1148, SEQ ID NO: 1149, SEQ ID        NO: 1150, SEQ ID NO: 1151, SEQ ID NO: 1152, SEQ ID NO: 1153, SEQ        ID NO: 1154, SEQ ID NO: 1155, SEQ ID NO: 1156, SEQ ID NO: 1157,        SEQ ID NO: 1158, SEQ ID NO: 1159, SEQ ID NO: 1160, SEQ ID NO:        1161, SEQ ID NO: 1162, SEQ ID NO: 1163, SEQ ID NO: 1164, SEQ ID        NO: 1165, SEQ ID NO: 1166, SEQ ID NO: 1167, SEQ ID NO: 1168, SEQ        ID NO: 1169, SEQ ID NO: 1170, SEQ ID NO: 1171, SEQ ID NO: 1172,        SEQ ID NO: 1173, SEQ ID NO: 1174, SEQ ID NO: 1175, SEQ ID NO:        1176, SEQ ID NO: 1177, SEQ ID NO: 1178, SEQ ID NO: 1179, SEQ ID        NO: 1180, SEQ ID NO: 1181, SEQ ID NO: 1182, SEQ ID NO: 1183, SEQ        ID NO: 1184, SEQ ID NO: 1185, SEQ ID NO: 1186, SEQ ID NO: 1187,        SEQ ID NO: 1188, SEQ ID NO: 1189, SEQ ID NO: 1190, SEQ ID NO:        1191, SEQ ID NO: 1192, SEQ ID NO: 1193, SEQ ID NO: 1194, SEQ ID        NO: 1195, SEQ ID NO: 1196, SEQ ID NO: 1197, SEQ ID NO: 1198, SEQ        ID NO: 1199, SEQ ID NO: 1200, SEQ ID NO: 1201, SEQ ID NO: 1202,        SEQ ID NO: 1203, SEQ ID NO: 1204, SEQ ID NO: 1205, SEQ ID NO:        1206, SEQ ID NO: 1207, SEQ ID NO: 1208, SEQ ID NO: 1209, SEQ ID        NO: 1210, SEQ ID NO: 1211, SEQ ID NO: 1212, SEQ ID NO: 1213, SEQ        ID NO: 1214, SEQ ID NO: 1215, SEQ ID NO: 1216, SEQ ID NO: 1217,        or SEQ ID NO: 1218.”    -   “SEQ ID NOs: 1429-1442” refers to “any one of SEQ ID NO: 1429,        SEQ ID NO: 1430, SEQ ID NO: 1431, SEQ ID NO: 1432, SEQ ID NO:        1433, SEQ ID NO: 1434, SEQ ID NO: 1435, SEQ ID NO: 1436, SEQ ID        NO: 1437, SEQ ID NO: 1438, SEQ ID NO: 1439, SEQ ID NO: 1440, SEQ        ID NO: 1441, or SEQ ID NO: 1442.”    -   “SEQ ID NOs: 1219-1428” refers to any one of SEQ ID NO: 1219,        SEQ ID NO: 1220, SEQ ID NO: 1221, SEQ ID NO: 1222, SEQ ID NO:        1223, SEQ ID NO: 1224, SEQ ID NO: 1225, SEQ ID NO: 1226, SEQ ID        NO: 1227, SEQ ID NO: 1228, SEQ ID NO: 1229, SEQ ID NO: 1230, SEQ        ID NO: 1231, SEQ ID NO: 1232, SEQ ID NO: 1233, SEQ ID NO: 1234,        SEQ ID NO: 1235, SEQ ID NO: 1236, SEQ ID NO: 1237, SEQ ID NO:        1238, SEQ ID NO: 1239, SEQ ID NO: 1240, SEQ ID NO: 1241, SEQ ID        NO: 1242, SEQ ID NO: 1243, SEQ ID NO: 1244, SEQ ID NO: 1245, SEQ        ID NO: 1246, SEQ ID NO: 1247, SEQ ID NO: 1248, SEQ ID NO: 1249,        SEQ ID NO: 1250, SEQ ID NO: 1251, SEQ ID NO: 1252, SEQ ID NO:        1253, SEQ ID NO: 1254, SEQ ID NO: 1255, SEQ ID NO: 1256, SEQ ID        NO: 1257, SEQ ID NO: 1258, SEQ ID NO: 1259, SEQ ID NO: 1260, SEQ        ID NO: 1261, SEQ ID NO: 1262, SEQ ID NO: 1263, SEQ ID NO: 1264,        SEQ ID NO: 1265, SEQ ID NO: 1266, SEQ ID NO: 1267, SEQ ID NO:        1268, SEQ ID NO: 1269, SEQ ID NO: 1270, SEQ ID NO: 1271, SEQ ID        NO: 1272, SEQ ID NO: 1273, SEQ ID NO: 1274, SEQ ID NO: 1275, SEQ        ID NO: 1276, SEQ ID NO: 1277, SEQ ID NO: 1278, SEQ ID NO: 1279,        SEQ ID NO: 1280, SEQ ID NO: 1281, SEQ ID NO: 1282, SEQ ID NO:        1283, SEQ ID NO: 1284, SEQ ID NO: 1285, SEQ ID NO: 1286, SEQ ID        NO: 1287, SEQ ID NO: 1288, SEQ ID NO: 1289, SEQ ID NO: 1290, SEQ        ID NO: 1291, SEQ ID NO: 1292, SEQ ID NO: 1293, SEQ ID NO: 1294,        SEQ ID NO: 1295, SEQ ID NO: 1296, SEQ ID NO: 1297, SEQ ID NO:        1298, SEQ ID NO: 1299, SEQ ID NO: 1300, SEQ ID NO: 1301, SEQ ID        NO: 1302, SEQ ID NO: 1303, SEQ ID NO: 1304, SEQ ID NO: 1305, SEQ        ID NO: 1306, SEQ ID NO: 1307, SEQ ID NO: 1308, SEQ ID NO: 1309,        SEQ ID NO: 1310, SEQ ID NO: 1311, SEQ ID NO: 1312, SEQ ID NO:        1313, SEQ ID NO: 1314, SEQ ID NO: 1315, SEQ ID NO: 1316, SEQ ID        NO: 1317, SEQ ID NO: 1318, SEQ ID NO: 1319, SEQ ID NO: 1320, SEQ        ID NO: 1321, SEQ ID NO: 1322, SEQ ID NO: 1323, SEQ ID NO: 1324,        SEQ ID NO: 1325, SEQ ID NO: 1326, SEQ ID NO: 1327, SEQ ID NO:        1328, SEQ ID NO: 1329, SEQ ID NO: 1330, SEQ ID NO: 1331, SEQ ID        NO: 1332, SEQ ID NO: 1333, SEQ ID NO: 1334, SEQ ID NO: 1335, SEQ        ID NO: 1336, SEQ ID NO: 1337, SEQ ID NO: 1338, SEQ ID NO: 1339,        SEQ ID NO: 1340, SEQ ID NO: 1341, SEQ ID NO: 1342, SEQ ID NO:        1343, SEQ ID NO: 1344, SEQ ID NO: 1345, SEQ ID NO: 1346, SEQ ID        NO: 1347, SEQ ID NO: 1348, SEQ ID NO: 1349, SEQ ID NO: 1350, SEQ        ID NO: 1351, SEQ ID NO: 1352, SEQ ID NO: 1353, SEQ ID NO: 1354,        SEQ ID NO: 1355, SEQ ID NO: 1356, SEQ ID NO: 1357, SEQ ID NO:        1358, SEQ ID NO: 1359, SEQ ID NO: 1360, SEQ ID NO: 1361, SEQ ID        NO: 1362, SEQ ID NO: 1363, SEQ ID NO: 1364, SEQ ID NO: 1365, SEQ        ID NO: 1366, SEQ ID NO: 1367, SEQ ID NO: 1368, SEQ ID NO: 1369,        SEQ ID NO: 1370, SEQ ID NO: 1371, SEQ ID NO: 1372, SEQ ID NO:        1373, SEQ ID NO: 1374, SEQ ID NO: 1375, SEQ ID NO: 1376, SEQ ID        NO: 1377, SEQ ID NO: 1378, SEQ ID NO: 1379, SEQ ID NO: 1380, SEQ        ID NO: 1381, SEQ ID NO: 1382, SEQ ID NO: 1383, SEQ ID NO: 1384,        SEQ ID NO: 1385, SEQ ID NO: 1386, SEQ ID NO: 1387, SEQ ID NO:        1388, SEQ ID NO: 1389, SEQ ID NO: 1390, SEQ ID NO: 1391, SEQ ID        NO: 1392, SEQ ID NO: 1393, SEQ ID NO: 1394, SEQ ID NO: 1395, SEQ        ID NO: 1396, SEQ ID NO: 1397, SEQ ID NO: 1398, SEQ ID NO: 1399,        SEQ ID NO: 1400, SEQ ID NO: 1401, SEQ ID NO: 1402, SEQ ID NO:        1403, SEQ ID NO: 1404, SEQ ID NO: 1405, SEQ ID NO: 1406, SEQ ID        NO: 1407, SEQ ID NO: 1408, SEQ ID NO: 1409, SEQ ID NO: 1410, SEQ        ID NO: 1411, SEQ ID NO: 1412, SEQ ID NO: 1413, SEQ ID NO: 1414,        SEQ ID NO: 1415, SEQ ID NO: 1416, SEQ ID NO: 1417, SEQ ID NO:        1418, SEQ ID NO: 1419, SEQ ID NO: 1420, SEQ ID NO: 1421, SEQ ID        NO: 1422, SEQ ID NO: 1423, SEQ ID NO: 1424, SEQ ID NO: 1425, SEQ        ID NO: 1426, SEQ ID NO: 1427, or SEQ ID NO: 1428.”

In some embodiments, a disclosed recombinant RSV F protein can includean amino acid sequence at least 80% (such as at least 90%, at least 95%,or at least 98%, or 100%) identical to any one of SEQ ID NO: 185, SEQ IDNO: 186, SEQ ID NO: 187, SEQ ID NO: 188, SEQ ID NO: 189, SEQ ID NO: 190,SEQ ID NO: 191, SEQ ID NO: 192, SEQ ID NO: 193, SEQ ID NO: 194, SEQ IDNO: 195, SEQ ID NO: 196, SEQ ID NO: 197, SEQ ID NO: 198, SEQ ID NO: 199,SEQ ID NO: 200, SEQ ID NO: 201, SEQ ID NO: 202, SEQ ID NO: 203, SEQ IDNO: 204, SEQ ID NO: 205, SEQ ID NO: 206, SEQ ID NO: 207, SEQ ID NO: 208,SEQ ID NO: 209, SEQ ID NO: 210, SEQ ID NO: 211, SEQ ID NO: 212, SEQ IDNO: 213, SEQ ID NO: 214, SEQ ID NO: 215, SEQ ID NO: 216, SEQ ID NO: 217,SEQ ID NO: 218, SEQ ID NO: 219, SEQ ID NO: 220, SEQ ID NO: 221, SEQ IDNO: 222, SEQ ID NO: 223, SEQ ID NO: 224, SEQ ID NO: 225, SEQ ID NO: 226,SEQ ID NO: 227, SEQ ID NO: 228, SEQ ID NO: 229, SEQ ID NO: 230, SEQ IDNO: 231, SEQ ID NO: 232, SEQ ID NO: 233, SEQ ID NO: 234, SEQ ID NO: 235,SEQ ID NO: 236, SEQ ID NO: 237, SEQ ID NO: 238, SEQ ID NO: 239, SEQ IDNO: 240, SEQ ID NO: 241, SEQ ID NO: 242, SEQ ID NO: 243, SEQ ID NO: 244,SEQ ID NO: 245, SEQ ID NO: 246, SEQ ID NO: 247, SEQ ID NO: 248, SEQ IDNO: 249, SEQ ID NO: 250, SEQ ID NO: 251, SEQ ID NO: 252, SEQ ID NO: 253,SEQ ID NO: 254, SEQ ID NO: 255, SEQ ID NO: 256, SEQ ID NO: 257, SEQ IDNO: 258, SEQ ID NO: 259, SEQ ID NO: 260, SEQ ID NO: 261, SEQ ID NO: 262,SEQ ID NO: 263, SEQ ID NO: 264, SEQ ID NO: 265, SEQ ID NO: 266, SEQ IDNO: 267, SEQ ID NO: 268, SEQ ID NO: 269, SEQ ID NO: 270, SEQ ID NO: 271,SEQ ID NO: 272, SEQ ID NO: 273, SEQ ID NO: 274, SEQ ID NO: 275, SEQ IDNO: 276, SEQ ID NO: 277, SEQ ID NO: 278, SEQ ID NO: 279, SEQ ID NO: 280,SEQ ID NO: 281, SEQ ID NO: 282, SEQ ID NO: 283, SEQ ID NO: 284, SEQ IDNO: 285, SEQ ID NO: 286, SEQ ID NO: 287, SEQ ID NO: 288, SEQ ID NO: 289,SEQ ID NO: 290, SEQ ID NO: 291, SEQ ID NO: 292, SEQ ID NO: 293, SEQ IDNO: 294, SEQ ID NO: 295, SEQ ID NO: 296, SEQ ID NO: 297, SEQ ID NO: 298,SEQ ID NO: 299, SEQ ID NO: 300, SEQ ID NO: 301, SEQ ID NO: 302, SEQ IDNO: 303, SEQ ID NO: 304, SEQ ID NO: 305, SEQ ID NO: 306, SEQ ID NO: 307,SEQ ID NO: 308, SEQ ID NO: 309, SEQ ID NO: 310, SEQ ID NO: 311, SEQ IDNO: 312, SEQ ID NO: 313, SEQ ID NO: 314, SEQ ID NO: 315, SEQ ID NO: 316,SEQ ID NO: 317, SEQ ID NO: 318, SEQ ID NO: 319, SEQ ID NO: 320, SEQ IDNO: 321, SEQ ID NO: 322, SEQ ID NO: 323, SEQ ID NO: 324, SEQ ID NO: 325,SEQ ID NO: 326, SEQ ID NO: 327, SEQ ID NO: 328, SEQ ID NO: 329, SEQ IDNO: 330, SEQ ID NO: 331, SEQ ID NO: 332, SEQ ID NO: 333, SEQ ID NO: 334,SEQ ID NO: 335, SEQ ID NO: 336, SEQ ID NO: 337, SEQ ID NO: 338, SEQ IDNO: 339, SEQ ID NO: 340, SEQ ID NO: 341, SEQ ID NO: 342, SEQ ID NO: 343,SEQ ID NO: 344, SEQ ID NO: 345, SEQ ID NO: 346, SEQ ID NO: 347, SEQ IDNO: 348, SEQ ID NO: 349, SEQ ID NO: 350, SEQ ID NO: 371, SEQ ID NO: 372,SEQ ID NO: 373, SEQ ID NO: 374, SEQ ID NO: 375, SEQ ID NO: 376, SEQ IDNO: 377, SEQ ID NO: 378, SEQ ID NO: 379, SEQ ID NO: 380, SEQ ID NO: 381,SEQ ID NO: 382, SEQ ID NO: 390, SEQ ID NO: 391, SEQ ID NO: 392, SEQ IDNO: 393, SEQ ID NO: 394, SEQ ID NO: 395, SEQ ID NO: 396, SEQ ID NO: 397,SEQ ID NO: 398, SEQ ID NO: 399, SEQ ID NO: 400, SEQ ID NO: 401, SEQ IDNO: 402, SEQ ID NO: 403, SEQ ID NO: 404, SEQ ID NO: 405, SEQ ID NO: 406,SEQ ID NO: 407, SEQ ID NO: 408, SEQ ID NO: 409, SEQ ID NO: 410, SEQ IDNO: 411, SEQ ID NO: 412, SEQ ID NO: 413, SEQ ID NO: 414, SEQ ID NO: 415,SEQ ID NO: 416, SEQ ID NO: 417, SEQ ID NO: 418, SEQ ID NO: 419, SEQ IDNO: 420, SEQ ID NO: 421, SEQ ID NO: 422, SEQ ID NO: 423, SEQ ID NO: 424,SEQ ID NO: 425, SEQ ID NO: 426, SEQ ID NO: 427, SEQ ID NO: 428, SEQ IDNO: 429, SEQ ID NO: 430, SEQ ID NO: 431, SEQ ID NO: 432, SEQ ID NO: 433,SEQ ID NO: 434, SEQ ID NO: 435, SEQ ID NO: 436, SEQ ID NO: 437, SEQ IDNO: 438, SEQ ID NO: 439, SEQ ID NO: 440, SEQ ID NO: 441, SEQ ID NO: 442,SEQ ID NO: 443, SEQ ID NO: 444, SEQ ID NO: 445, SEQ ID NO: 446, SEQ IDNO: 447, SEQ ID NO: 448, SEQ ID NO: 449, SEQ ID NO: 450, SEQ ID NO: 451,SEQ ID NO: 452, SEQ ID NO: 453, SEQ ID NO: 454, SEQ ID NO: 455, SEQ IDNO: 456, SEQ ID NO: 457, SEQ ID NO: 458, SEQ ID NO: 459, SEQ ID NO: 460,SEQ ID NO: 461, SEQ ID NO: 462, SEQ ID NO: 463, SEQ ID NO: 464, SEQ IDNO: 465, SEQ ID NO: 466, SEQ ID NO: 467, SEQ ID NO: 468, SEQ ID NO: 469,SEQ ID NO: 470, SEQ ID NO: 471, SEQ ID NO: 472, SEQ ID NO: 473, SEQ IDNO: 474, SEQ ID NO: 475, SEQ ID NO: 476, SEQ ID NO: 477, SEQ ID NO: 478,SEQ ID NO: 479, SEQ ID NO: 480, SEQ ID NO: 481, SEQ ID NO: 482, SEQ IDNO: 483, SEQ ID NO: 484, SEQ ID NO: 485, SEQ ID NO: 486, SEQ ID NO: 487,SEQ ID NO: 488, SEQ ID NO: 489, SEQ ID NO: 490, SEQ ID NO: 491, SEQ IDNO: 492, SEQ ID NO: 493, SEQ ID NO: 494, SEQ ID NO: 495, SEQ ID NO: 496,SEQ ID NO: 497, SEQ ID NO: 498, SEQ ID NO: 499, SEQ ID NO: 500, SEQ IDNO: 501, SEQ ID NO: 502, SEQ ID NO: 503, SEQ ID NO: 504, SEQ ID NO: 505,SEQ ID NO: 506, SEQ ID NO: 507, SEQ ID NO: 508, SEQ ID NO: 509, SEQ IDNO: 510, SEQ ID NO: 511, SEQ ID NO: 512, SEQ ID NO: 513, SEQ ID NO: 514,SEQ ID NO: 515, SEQ ID NO: 516, SEQ ID NO: 517, SEQ ID NO: 518, SEQ IDNO: 519, SEQ ID NO: 520, SEQ ID NO: 521, SEQ ID NO: 522, SEQ ID NO: 523,SEQ ID NO: 524, SEQ ID NO: 525, SEQ ID NO: 526, SEQ ID NO: 527, SEQ IDNO: 528, SEQ ID NO: 529, SEQ ID NO: 530, SEQ ID NO: 531, SEQ ID NO: 532,SEQ ID NO: 533, SEQ ID NO: 534, SEQ ID NO: 535, SEQ ID NO: 536, SEQ IDNO: 537, SEQ ID NO: 538, SEQ ID NO: 539, SEQ ID NO: 540, SEQ ID NO: 541,SEQ ID NO: 542, SEQ ID NO: 543, SEQ ID NO: 544, SEQ ID NO: 545, SEQ IDNO: 546, SEQ ID NO: 547, SEQ ID NO: 548, SEQ ID NO: 549, SEQ ID NO: 550,SEQ ID NO: 551, SEQ ID NO: 552, SEQ ID NO: 553, SEQ ID NO: 554, SEQ IDNO: 555, SEQ ID NO: 556, SEQ ID NO: 557, SEQ ID NO: 558, SEQ ID NO: 559,SEQ ID NO: 560, SEQ ID NO: 561, SEQ ID NO: 562, SEQ ID NO: 563, SEQ IDNO: 564, SEQ ID NO: 565, SEQ ID NO: 566, SEQ ID NO: 567, SEQ ID NO: 568,SEQ ID NO: 569, SEQ ID NO: 570, SEQ ID NO: 571, SEQ ID NO: 572, SEQ IDNO: 573, SEQ ID NO: 574, SEQ ID NO: 575, SEQ ID NO: 576, SEQ ID NO: 577,SEQ ID NO: 578, SEQ ID NO: 579, SEQ ID NO: 580, SEQ ID NO: 581, SEQ IDNO: 582, SEQ ID NO: 583, SEQ ID NO: 584, SEQ ID NO: 585, SEQ ID NO: 586,SEQ ID NO: 587, SEQ ID NO: 588, SEQ ID NO: 589, SEQ ID NO: 590, SEQ IDNO: 591, SEQ ID NO: 592, SEQ ID NO: 593, SEQ ID NO: 594, SEQ ID NO: 595,SEQ ID NO: 596, SEQ ID NO: 597, SEQ ID NO: 598, SEQ ID NO: 599, SEQ IDNO: 600, SEQ ID NO: 601, SEQ ID NO: 602, SEQ ID NO: 603, SEQ ID NO: 604,SEQ ID NO: 605, SEQ ID NO: 606, SEQ ID NO: 607, SEQ ID NO: 608, SEQ IDNO: 609, SEQ ID NO: 610, SEQ ID NO: 611, SEQ ID NO: 612, SEQ ID NO: 613,SEQ ID NO: 614, SEQ ID NO: 615, SEQ ID NO: 616, SEQ ID NO: 617, SEQ IDNO: 618, SEQ ID NO: 619, SEQ ID NO: 620, SEQ ID NO: 621, SEQ ID NO: 622,SEQ ID NO: 623, SEQ ID NO: 624, SEQ ID NO: 625, SEQ ID NO: 626, SEQ IDNO: 627, SEQ ID NO: 628, SEQ ID NO: 629, SEQ ID NO: 630, SEQ ID NO: 631,SEQ ID NO: 632, SEQ ID NO: 633, SEQ ID NO: 634, SEQ ID NO: 635, SEQ IDNO: 636, SEQ ID NO: 637, SEQ ID NO: 638, SEQ ID NO: 639, SEQ ID NO: 640,SEQ ID NO: 641, SEQ ID NO: 642, SEQ ID NO: 643, SEQ ID NO: 644, SEQ IDNO: 645, SEQ ID NO: 646, SEQ ID NO: 647, SEQ ID NO: 648, SEQ ID NO: 649,SEQ ID NO: 650, SEQ ID NO: 651, SEQ ID NO: 652, SEQ ID NO: 653, SEQ IDNO: 654, SEQ ID NO: 655, SEQ ID NO: 656, SEQ ID NO: 657, SEQ ID NO: 658,SEQ ID NO: 659, SEQ ID NO: 660, SEQ ID NO: 661, SEQ ID NO: 662, SEQ IDNO: 663, SEQ ID NO: 664, SEQ ID NO: 665, SEQ ID NO: 666, SEQ ID NO: 667,SEQ ID NO: 668, SEQ ID NO: 669, SEQ ID NO: 670, SEQ ID NO: 671, SEQ IDNO: 672, SEQ ID NO: 673, SEQ ID NO: 674, SEQ ID NO: 675, SEQ ID NO: 676,SEQ ID NO: 677, SEQ ID NO: 678, SEQ ID NO: 679, SEQ ID NO: 680, SEQ IDNO: 681, SEQ ID NO: 682, SEQ ID NO: 683, SEQ ID NO: 684, SEQ ID NO: 685,SEQ ID NO: 686, SEQ ID NO: 687, SEQ ID NO: 688, SEQ ID NO: 689, SEQ IDNO: 690, SEQ ID NO: 691, SEQ ID NO: 692, SEQ ID NO: 693, SEQ ID NO: 698,SEQ ID NO: 699, SEQ ID NO: 700, SEQ ID NO: 701, SEQ ID NO: 702, SEQ IDNO: 703, SEQ ID NO: 704, SEQ ID NO: 705, SEQ ID NO: 706, SEQ ID NO: 707,SEQ ID NO: 708, SEQ ID NO: 709, SEQ ID NO: 710, SEQ ID NO: 711, SEQ IDNO: 712, SEQ ID NO: 713, SEQ ID NO: 714, SEQ ID NO: 715, SEQ ID NO: 716,SEQ ID NO: 717, SEQ ID NO: 718, SEQ ID NO: 719, SEQ ID NO: 720, SEQ IDNO: 721, SEQ ID NO: 722, SEQ ID NO: 723, SEQ ID NO: 724, SEQ ID NO: 725,SEQ ID NO: 726, SEQ ID NO: 727, SEQ ID NO: 728, SEQ ID NO: 729, SEQ IDNO: 730, SEQ ID NO: 731, SEQ ID NO: 732, SEQ ID NO: 733, SEQ ID NO: 734,SEQ ID NO: 735, SEQ ID NO: 736, SEQ ID NO: 737, SEQ ID NO: 738, SEQ IDNO: 739, SEQ ID NO: 740, SEQ ID NO: 741, SEQ ID NO: 742, SEQ ID NO: 743,SEQ ID NO: 744, SEQ ID NO: 745, SEQ ID NO: 746, SEQ ID NO: 747, SEQ IDNO: 748, SEQ ID NO: 749, SEQ ID NO: 750, SEQ ID NO: 751, SEQ ID NO: 752,SEQ ID NO: 753, SEQ ID NO: 754, SEQ ID NO: 755, SEQ ID NO: 756, SEQ IDNO: 757, SEQ ID NO: 758, SEQ ID NO: 759, SEQ ID NO: 760, SEQ ID NO: 761,SEQ ID NO: 762, SEQ ID NO: 763, SEQ ID NO: 764, SEQ ID NO: 765, SEQ IDNO: 766, SEQ ID NO: 767, SEQ ID NO: 768, SEQ ID NO: 769, SEQ ID NO: 770,SEQ ID NO: 771, SEQ ID NO: 772, SEQ ID NO: 773, SEQ ID NO: 774, SEQ IDNO: 775, SEQ ID NO: 776, SEQ ID NO: 777, SEQ ID NO: 778, SEQ ID NO: 779,SEQ ID NO: 780, SEQ ID NO: 781, SEQ ID NO: 782, SEQ ID NO: 783, SEQ IDNO: 784, SEQ ID NO: 785, SEQ ID NO: 786, SEQ ID NO: 787, SEQ ID NO: 788,SEQ ID NO: 789, SEQ ID NO: 790, SEQ ID NO: 791, SEQ ID NO: 792, SEQ IDNO: 793, SEQ ID NO: 794, SEQ ID NO: 795, SEQ ID NO: 796, SEQ ID NO: 797,SEQ ID NO: 798, SEQ ID NO: 799, SEQ ID NO: 800, SEQ ID NO: 801, SEQ IDNO: 802, SEQ ID NO: 803, SEQ ID NO: 804, SEQ ID NO: 805, SEQ ID NO: 806,SEQ ID NO: 807, SEQ ID NO: 808, SEQ ID NO: 809, SEQ ID NO: 810, SEQ IDNO: 811, SEQ ID NO: 812, SEQ ID NO: 813, SEQ ID NO: 814, SEQ ID NO: 815,SEQ ID NO: 816, SEQ ID NO: 817, SEQ ID NO: 818, SEQ ID NO: 819, SEQ IDNO: 820, SEQ ID NO: 821, SEQ ID NO: 822, SEQ ID NO: 823, SEQ ID NO: 824,SEQ ID NO: 825, SEQ ID NO: 826, SEQ ID NO: 827, SEQ ID NO: 828, SEQ IDNO: 829, SEQ ID NO: 830, SEQ ID NO: 831, SEQ ID NO: 832, SEQ ID NO: 833,SEQ ID NO: 834, SEQ ID NO: 835, SEQ ID NO: 836, SEQ ID NO: 837, SEQ IDNO: 838, SEQ ID NO: 839, SEQ ID NO: 840, SEQ ID NO: 841, SEQ ID NO: 842,SEQ ID NO: 843, SEQ ID NO: 844, SEQ ID NO: 845, SEQ ID NO: 846, SEQ IDNO: 847, SEQ ID NO: 848, SEQ ID NO: 849, SEQ ID NO: 850, SEQ ID NO: 851,SEQ ID NO: 852, SEQ ID NO: 853, SEQ ID NO: 854, SEQ ID NO: 855, SEQ IDNO: 856, SEQ ID NO: 857, SEQ ID NO: 858, SEQ ID NO: 859, SEQ ID NO: 860,SEQ ID NO: 861, SEQ ID NO: 862, SEQ ID NO: 863, SEQ ID NO: 864, SEQ IDNO: 865, SEQ ID NO: 866, SEQ ID NO: 867, SEQ ID NO: 868, SEQ ID NO: 869,SEQ ID NO: 870, SEQ ID NO: 871, SEQ ID NO: 872, SEQ ID NO: 873, SEQ IDNO: 874, SEQ ID NO: 875, SEQ ID NO: 876, SEQ ID NO: 877, SEQ ID NO: 878,SEQ ID NO: 879, SEQ ID NO: 880, SEQ ID NO: 881, SEQ ID NO: 882, SEQ IDNO: 883, SEQ ID NO: 884, SEQ ID NO: 885, SEQ ID NO: 886, SEQ ID NO: 887,SEQ ID NO: 888, SEQ ID NO: 889, SEQ ID NO: 890, SEQ ID NO: 891, SEQ IDNO: 892, SEQ ID NO: 893, SEQ ID NO: 894, SEQ ID NO: 895, SEQ ID NO: 896,SEQ ID NO: 897, SEQ ID NO: 898, SEQ ID NO: 899, SEQ ID NO: 900, SEQ IDNO: 901, SEQ ID NO: 902, SEQ ID NO: 903, SEQ ID NO: 904, SEQ ID NO: 905,SEQ ID NO: 906, SEQ ID NO: 907, SEQ ID NO: 908, SEQ ID NO: 909, SEQ IDNO: 910, SEQ ID NO: 911, SEQ ID NO: 912, SEQ ID NO: 913, SEQ ID NO: 914,SEQ ID NO: 915, SEQ ID NO: 916, SEQ ID NO: 917, SEQ ID NO: 918, SEQ IDNO: 919, SEQ ID NO: 920, SEQ ID NO: 921, SEQ ID NO: 922, SEQ ID NO: 923,SEQ ID NO: 924, SEQ ID NO: 925, SEQ ID NO: 926, SEQ ID NO: 927, SEQ IDNO: 928, SEQ ID NO: 929, SEQ ID NO: 930, SEQ ID NO: 931, SEQ ID NO: 932,SEQ ID NO: 933, SEQ ID NO: 934, SEQ ID NO: 935, SEQ ID NO: 936, SEQ IDNO: 937, SEQ ID NO: 938, SEQ ID NO: 939, SEQ ID NO: 940, SEQ ID NO: 941,SEQ ID NO: 942, SEQ ID NO: 943, SEQ ID NO: 944, SEQ ID NO: 945, SEQ IDNO: 946, SEQ ID NO: 947, SEQ ID NO: 948, SEQ ID NO: 949, SEQ ID NO: 950,SEQ ID NO: 951, SEQ ID NO: 952, SEQ ID NO: 953, SEQ ID NO: 954, SEQ IDNO: 955, SEQ ID NO: 956, SEQ ID NO: 957, SEQ ID NO: 958, SEQ ID NO: 959,SEQ ID NO: 960, SEQ ID NO: 961, SEQ ID NO: 962, SEQ ID NO: 963, SEQ IDNO: 964, SEQ ID NO: 965, SEQ ID NO: 966, SEQ ID NO: 967, SEQ ID NO: 968,SEQ ID NO: 969, SEQ ID NO: 970, SEQ ID NO: 971, SEQ ID NO: 972, SEQ IDNO: 973, SEQ ID NO: 974, SEQ ID NO: 975, SEQ ID NO: 976, SEQ ID NO: 977,SEQ ID NO: 978, SEQ ID NO: 979, SEQ ID NO: 980, SEQ ID NO: 981, SEQ IDNO: 982, SEQ ID NO: 983, SEQ ID NO: 984, SEQ ID NO: 985, SEQ ID NO: 986,SEQ ID NO: 987, SEQ ID NO: 988, SEQ ID NO: 989, SEQ ID NO: 990, SEQ IDNO: 991, SEQ ID NO: 992, SEQ ID NO: 993, SEQ ID NO: 994, SEQ ID NO: 995,SEQ ID NO: 996, SEQ ID NO: 997, SEQ ID NO: 998, SEQ ID NO: 999, SEQ IDNO: 1000, SEQ ID NO: 1001, SEQ ID NO: 1002, SEQ ID NO: 1003, SEQ ID NO:1004, SEQ ID NO: 1005, SEQ ID NO: 1006, SEQ ID NO: 1007, SEQ ID NO:1008, SEQ ID NO: 1009, SEQ ID NO: 1010, SEQ ID NO: 1011, SEQ ID NO:1012, SEQ ID NO: 1013, SEQ ID NO: 1014, SEQ ID NO: 1015, SEQ ID NO:1016, SEQ ID NO: 1017, SEQ ID NO: 1018, SEQ ID NO: 1019, SEQ ID NO:1020, SEQ ID NO: 1021, SEQ ID NO: 1022, SEQ ID NO: 1023, SEQ ID NO:1024, SEQ ID NO: 1025, SEQ ID NO: 1026, SEQ ID NO: 1027, SEQ ID NO:1028, SEQ ID NO: 1029, SEQ ID NO: 1030, SEQ ID NO: 1031, SEQ ID NO:1032, SEQ ID NO: 1033, SEQ ID NO: 1034, SEQ ID NO: 1035, SEQ ID NO:1036, SEQ ID NO: 1037, SEQ ID NO: 1038, SEQ ID NO: 1039, SEQ ID NO:1040, SEQ ID NO: 1041, SEQ ID NO: 1042, SEQ ID NO: 1043, SEQ ID NO:1044, SEQ ID NO: 1045, SEQ ID NO: 1046, SEQ ID NO: 1047, SEQ ID NO:1048, SEQ ID NO: 1049, SEQ ID NO: 1050, SEQ ID NO: 1051, SEQ ID NO:1052, SEQ ID NO: 1053, SEQ ID NO: 1054, SEQ ID NO: 1055, SEQ ID NO:1056, SEQ ID NO: 1057, SEQ ID NO: 1058, SEQ ID NO: 1059, SEQ ID NO:1060, SEQ ID NO: 1061, SEQ ID NO: 1062, SEQ ID NO: 1063, SEQ ID NO:1064, SEQ ID NO: 1065, SEQ ID NO: 1066, SEQ ID NO: 1067, SEQ ID NO:1068, SEQ ID NO: 1069, SEQ ID NO: 1070, SEQ ID NO: 1071, SEQ ID NO:1072, SEQ ID NO: 1073, SEQ ID NO: 1074, SEQ ID NO: 1075, SEQ ID NO:1076, SEQ ID NO: 1077, SEQ ID NO: 1078, SEQ ID NO: 1079, SEQ ID NO:1080, SEQ ID NO: 1081, SEQ ID NO: 1082, SEQ ID NO: 1083, SEQ ID NO:1084, SEQ ID NO: 1085, SEQ ID NO: 1086, SEQ ID NO: 1087, SEQ ID NO:1088, SEQ ID NO: 1099, SEQ ID NO: 1100, SEQ ID NO: 1101, SEQ ID NO:1102, SEQ ID NO: 1103, SEQ ID NO: 1104, SEQ ID NO: 1105, SEQ ID NO:1106, SEQ ID NO: 1107, SEQ ID NO: 1108, SEQ ID NO: 1109, SEQ ID NO:1110, SEQ ID NO: 1111, SEQ ID NO: 1112, SEQ ID NO: 1113, SEQ ID NO:1114, SEQ ID NO: 1115, SEQ ID NO: 1116, SEQ ID NO: 1117, SEQ ID NO:1118, SEQ ID NO: 1119, SEQ ID NO: 1120, SEQ ID NO: 1121, SEQ ID NO:1122, SEQ ID NO: 1123, SEQ ID NO: 1124, SEQ ID NO: 1125, SEQ ID NO:1126, SEQ ID NO: 1127, SEQ ID NO: 1128, SEQ ID NO: 1129, SEQ ID NO:1130, SEQ ID NO: 1131, SEQ ID NO: 1132, SEQ ID NO: 1133, SEQ ID NO:1134, SEQ ID NO: 1135, SEQ ID NO: 1136, SEQ ID NO: 1137, SEQ ID NO:1138, SEQ ID NO: 1139, SEQ ID NO: 1140, SEQ ID NO: 1141, SEQ ID NO:1142, SEQ ID NO: 1143, SEQ ID NO: 1144, SEQ ID NO: 1145, SEQ ID NO:1146, SEQ ID NO: 1147, SEQ ID NO: 1148, SEQ ID NO: 1149, SEQ ID NO:1150, SEQ ID NO: 1151, SEQ ID NO: 1152, SEQ ID NO: 1153, SEQ ID NO:1154, SEQ ID NO: 1155, SEQ ID NO: 1156, SEQ ID NO: 1157, SEQ ID NO:1158, SEQ ID NO: 1159, SEQ ID NO: 1160, SEQ ID NO: 1161, SEQ ID NO:1162, SEQ ID NO: 1163, SEQ ID NO: 1164, SEQ ID NO: 1165, SEQ ID NO:1166, SEQ ID NO: 1167, SEQ ID NO: 1168, SEQ ID NO: 1169, SEQ ID NO:1170, SEQ ID NO: 1171, SEQ ID NO: 1172, SEQ ID NO: 1173, SEQ ID NO:1174, SEQ ID NO: 1175, SEQ ID NO: 1176, SEQ ID NO: 1177, SEQ ID NO:1178, SEQ ID NO: 1179, SEQ ID NO: 1180, SEQ ID NO: 1181, SEQ ID NO:1182, SEQ ID NO: 1183, SEQ ID NO: 1184, SEQ ID NO: 1185, SEQ ID NO:1186, SEQ ID NO: 1187, SEQ ID NO: 1188, SEQ ID NO: 1189, SEQ ID NO:1190, SEQ ID NO: 1191, SEQ ID NO: 1192, SEQ ID NO: 1193, SEQ ID NO:1194, SEQ ID NO: 1195, SEQ ID NO: 1196, SEQ ID NO: 1197, SEQ ID NO:1198, SEQ ID NO: 1199, SEQ ID NO: 1200, SEQ ID NO: 1201, SEQ ID NO:1202, SEQ ID NO: 1203, SEQ ID NO: 1204, SEQ ID NO: 1205, SEQ ID NO:1206, SEQ ID NO: 1207, SEQ ID NO: 1208, SEQ ID NO: 1209, SEQ ID NO:1210, SEQ ID NO: 1211, SEQ ID NO: 1212, SEQ ID NO: 1213, SEQ ID NO:1214, SEQ ID NO: 1215, SEQ ID NO: 1216, SEQ ID NO: 1217, SEQ ID NO:1218, SEQ ID NO: 1219, SEQ ID NO: 1220, SEQ ID NO: 1221, SEQ ID NO:1222, SEQ ID NO: 1223, SEQ ID NO: 1224, SEQ ID NO: 1225, SEQ ID NO:1226, SEQ ID NO: 1227, SEQ ID NO: 1228, SEQ ID NO: 1229, SEQ ID NO:1230, SEQ ID NO: 1231, SEQ ID NO: 1232, SEQ ID NO: 1233, SEQ ID NO:1234, SEQ ID NO: 1235, SEQ ID NO: 1236, SEQ ID NO: 1237, SEQ ID NO:1238, SEQ ID NO: 1239, SEQ ID NO: 1240, SEQ ID NO: 1241, SEQ ID NO:1242, SEQ ID NO: 1243, SEQ ID NO: 1244, SEQ ID NO: 1245, SEQ ID NO:1246, SEQ ID NO: 1247, SEQ ID NO: 1248, SEQ ID NO: 1249, SEQ ID NO:1250, SEQ ID NO: 1251, SEQ ID NO: 1252, SEQ ID NO: 1253, SEQ ID NO:1254, SEQ ID NO: 1255, SEQ ID NO: 1256, SEQ ID NO: 1257, SEQ ID NO:1258, SEQ ID NO: 1259, SEQ ID NO: 1260, SEQ ID NO: 1261, SEQ ID NO:1262, SEQ ID NO: 1263, SEQ ID NO: 1264, SEQ ID NO: 1265, SEQ ID NO:1266, SEQ ID NO: 1267, SEQ ID NO: 1268, SEQ ID NO: 1269, SEQ ID NO:1270, SEQ ID NO: 1271, SEQ ID NO: 1272, SEQ ID NO: 1273, SEQ ID NO:1274, SEQ ID NO: 1275, SEQ ID NO: 1276, SEQ ID NO: 1277, SEQ ID NO:1278, SEQ ID NO: 1279, SEQ ID NO: 1280, SEQ ID NO: 1281, SEQ ID NO:1282, SEQ ID NO: 1283, SEQ ID NO: 1284, SEQ ID NO: 1285, SEQ ID NO:1286, SEQ ID NO: 1287, SEQ ID NO: 1288, SEQ ID NO: 1289, SEQ ID NO:1290, SEQ ID NO: 1291, SEQ ID NO: 1292, SEQ ID NO: 1293, SEQ ID NO:1294, SEQ ID NO: 1295, SEQ ID NO: 1296, SEQ ID NO: 1297, SEQ ID NO:1298, SEQ ID NO: 1299, SEQ ID NO: 1300, SEQ ID NO: 1301, SEQ ID NO:1302, SEQ ID NO: 1303, SEQ ID NO: 1304, SEQ ID NO: 1305, SEQ ID NO:1306, SEQ ID NO: 1307, SEQ ID NO: 1308, SEQ ID NO: 1309, SEQ ID NO:1310, SEQ ID NO: 1311, SEQ ID NO: 1312, SEQ ID NO: 1313, SEQ ID NO:1314, SEQ ID NO: 1315, SEQ ID NO: 1316, SEQ ID NO: 1317, SEQ ID NO:1318, SEQ ID NO: 1319, SEQ ID NO: 1320, SEQ ID NO: 1321, SEQ ID NO:1322, SEQ ID NO: 1323, SEQ ID NO: 1324, SEQ ID NO: 1325, SEQ ID NO:1326, SEQ ID NO: 1327, SEQ ID NO: 1328, SEQ ID NO: 1329, SEQ ID NO:1330, SEQ ID NO: 1331, SEQ ID NO: 1332, SEQ ID NO: 1333, SEQ ID NO:1334, SEQ ID NO: 1335, SEQ ID NO: 1336, SEQ ID NO: 1337, SEQ ID NO:1338, SEQ ID NO: 1339, SEQ ID NO: 1340, SEQ ID NO: 1341, SEQ ID NO:1342, SEQ ID NO: 1343, SEQ ID NO: 1344, SEQ ID NO: 1345, SEQ ID NO:1346, SEQ ID NO: 1347, SEQ ID NO: 1348, SEQ ID NO: 1349, SEQ ID NO:1350, SEQ ID NO: 1351, SEQ ID NO: 1352, SEQ ID NO: 1353, SEQ ID NO:1354, SEQ ID NO: 1355, SEQ ID NO: 1356, SEQ ID NO: 1357, SEQ ID NO:1358, SEQ ID NO: 1359, SEQ ID NO: 1360, SEQ ID NO: 1361, SEQ ID NO:1362, SEQ ID NO: 1363, SEQ ID NO: 1364, SEQ ID NO: 1365, SEQ ID NO:1366, SEQ ID NO: 1367, SEQ ID NO: 1368, SEQ ID NO: 1369, SEQ ID NO:1370, SEQ ID NO: 1371, SEQ ID NO: 1372, SEQ ID NO: 1373, SEQ ID NO:1374, SEQ ID NO: 1375, SEQ ID NO: 1376, SEQ ID NO: 1377, SEQ ID NO:1378, SEQ ID NO: 1379, SEQ ID NO: 1380, SEQ ID NO: 1381, SEQ ID NO:1382, SEQ ID NO: 1383, SEQ ID NO: 1384, SEQ ID NO: 1385, SEQ ID NO:1386, SEQ ID NO: 1387, SEQ ID NO: 1388, SEQ ID NO: 1389, SEQ ID NO:1390, SEQ ID NO: 1391, SEQ ID NO: 1392, SEQ ID NO: 1393, SEQ ID NO:1394, SEQ ID NO: 1395, SEQ ID NO: 1396, SEQ ID NO: 1397, SEQ ID NO:1398, SEQ ID NO: 1399, SEQ ID NO: 1400, SEQ ID NO: 1401, SEQ ID NO:1402, SEQ ID NO: 1403, SEQ ID NO: 1404, SEQ ID NO: 1405, SEQ ID NO:1406, SEQ ID NO: 1407, SEQ ID NO: 1408, SEQ ID NO: 1409, SEQ ID NO:1410, SEQ ID NO: 1411, SEQ ID NO: 1412, SEQ ID NO: 1413, SEQ ID NO:1414, SEQ ID NO: 1415, SEQ ID NO: 1416, SEQ ID NO: 1417, SEQ ID NO:1418, SEQ ID NO: 1419, SEQ ID NO: 1420, SEQ ID NO: 1421, SEQ ID NO:1422, SEQ ID NO: 1423, SEQ ID NO: 1424, SEQ ID NO: 1425, SEQ ID NO:1426, SEQ ID NO: 1427, SEQ ID NO: 1428, SEQ ID NO: 1429, SEQ ID NO:1430, SEQ ID NO: 1431, SEQ ID NO: 1432, SEQ ID NO: 1433, SEQ ID NO:1434, SEQ ID NO: 1435, SEQ ID NO: 1436, SEQ ID NO: 1437, SEQ ID NO:1438, SEQ ID NO: 1439, SEQ ID NO: 1440, SEQ ID NO: 1441, SEQ ID NO:1442, SEQ ID NO: 1456, SEQ ID NO: 1457, SEQ ID NO: 1458, SEQ ID NO:1459, SEQ ID NO: 1460, SEQ ID NO: 1461, SEQ ID NO: 1462, SEQ ID NO:1463, SEQ ID NO: 1464, SEQ ID NO: 1465, SEQ ID NO: 1466, SEQ ID NO:1467, SEQ ID NO: 1468, SEQ ID NO: 1474, SEQ ID NO: 1475, SEQ ID NO:1476, SEQ ID NO: 1477, or SEQ ID NO: 1478 (“Sequence set F”), whereinthe recombinant RSV F polypeptide specifically binds to a RSV Fprefusion specific antibody (such as D25) and/or includes a RSV Fprefusion specific antigenic site (such as antigenic site Ø). In severalembodiments the immunogen specifically binds to the antibody or includesthe antigenic site after incubation in PBS at pH 7.4 at 20° C. for 24hours. In some embodiments, the recombinant RSV F polypeptide includesone of the sequences from Sequence set F, and further includes up to 20(such as up to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, or 19) amino acid substitutions (such as conservative amino acidsubstitutions, wherein the recombinant RSV F polypeptide specificallybinds to a RSV F prefusion specific antibody (such as D25) and/orincludes a RSV F prefusion specific antigenic site (such as antigenicsite Ø). The person of ordinary skill in the art will appreciate thatthe sequences listed above may include leader sequences, purificationtags, protease cleavage sites to remove purification tags trimerizationdomains, protein nanoparticle subunit domains or other sequences thatare unrelated to the recombinant RSV F protein. In several embodiments,an immunogen provided herein includes a recombinant RSV F protein of oneof the above sequences but does not include the leader sequences,purification tags, protease cleavage sites to remove purification tagstrimerization domains, protein nanoparticle subunit domains or othersequences that are unrelated to the recombinant RSV F protein. Nucleicacid molecules encoding these protein sequences are also provides, asare methods of using the recombinant RSV F proteins to generate animmune response to RSV in a subject, or to prevent or treat RSVinfection in a subject.

III. EXAMPLES

The following examples are provided to illustrate particular features ofcertain embodiments, but the scope of the claims should not be limitedto those features exemplified.

Example 1 Structure of Respiratory Syncytial Virus Prefusion F TrimerBound to a Human Antibody

The prefusion conformation of the respiratory syncytial virus (RSV)fusion (F) glycoprotein is the target of most RSV-neutralizingantibodies in human sera, but its metastability has hinderedcharacterization. To overcome this obstacle, antibodies that do not bindthe postfusion conformation of F and are >10-fold more potent than theprophylactic antibody palivizumab (Synagis®), were identified. Theco-crystal structure for one of these antibodies, D25, in complex withthe F glycoprotein reveals that D25 locks F in its prefusion state.Comparisons of prefusion and postfusion F conformations define therearrangements required to mediate RSV entry. The D25-F glycoproteinstructure reveals a new site-of-vulnerability, antigenic site Ø, at thetop of the F glycoprotein that is prefusion-specific and quaternary incharacter. The prefusion RSV F trimer structure, along with definitionof antigenic site Ø, should enable the design of improved vaccineantigens and guide new approaches for passive prevention of RSV-induceddisease.

Respiratory syncytial virus (RSV) is ubiquitous, infecting nearly allchildren by 3 years of age (Glezen et al., Am. J. Dis. Child., 140, 543(1986)). In the US, RSV bronchiolitis is the leading cause ofhospitalization in infants and a major cause of asthma and wheezingthroughout childhood (Shay et al., JAMA, 282, 1440 (1999); Hall et al.,N. Engl. J. Med., 360, 588 (2009)). Globally, RSV is responsible for66,000-199,000 deaths each year for children younger than five years ofage (Nair et al., Lancet, 375, 1545 (2010)), and accounts for 7% ofdeaths among infants 1 month to 1 year old-more than any other singlepathogen except malaria (Lozano et al., Lancet, 380, 2095 (2013)). Theonly available intervention is passive administration of the licensedmonoclonal antibody palivizumab (Synagis®), which recognizes the RSVfusion (F) glycoprotein (Johnson et al., J. Infect. Dis., 176, 1215(1997); Beeler and van Wyke Coelingh, J. Virol., 63, 2941 (1989)) andreduces incidence of severe disease (The IMpact-RSV Study Group,Pediatrics, 102, 531 (1998)). Clinical evidence that RSV F-specificantibodies can protect against disease has prompted a search for betterantibodies (Collarini et al., J. Immunol., 183, 6338 (2009); Wu et al.,J. Mol. Biol., 368, 652 (2007); Kwakkenbos et al., Nat. Med., 16, 123(2010)) and a concerted effort to develop an effective vaccine (Graham,Immunol. Rev., 239, 149 (2011)).

The RSV F glycoprotein facilitates fusion of viral and cellularmembranes (Walsh and Hruska, J. Virol., 47, 171 (1983)); it is a type Ifusion protein, with a metastable prefusion conformation that storesfolding energy, released during a structural rearrangement to a highlystable postfusion conformation. Three antigenic sites (I, II, and IV)have been found to elicit neutralizing activity (Arbiza et al., J. Gen.Virol., 73, 2225 (1992); Lopez et al., J. Virol., 72, 6922 (1998); Lópezet al., J. Virol., 64, 927 (1990)), and all exist on the postfusion formof F as determined by structural and biophysical studies (McLellan etal., J. Virol., 85, 7788 (2011); Swanson et al., Proc. Natl. Acad. Sci.U.S.A., 108, 9619 (2011)). Absorption of human sera with postfusion F,however, fails to remove the majority of F-specific neutralizingactivity, suggesting that the prefusion form may harbor novelneutralizing antigenic sites (Magro et al., Proc. Natl. Acad. Sci.U.S.A., 109, 3089 (2012)). Despite extensive effort, a homogeneouspreparation of soluble prefusion RSV F has not been obtained. Thus,determination of the prefusion F structure and identification of novelF-specific antigenic sites have become converging priorities fordevelopment of new prophylactic and therapeutic antibodies and vaccines.In line with these objectives, F-specific antibodies that couldneutralize RSV, but not bind to postfusion F were identified, andstructure of RSV F recognized by these antibodies was defined. Theresults reveal the prefusion conformation of RSV F, the mechanism ofneutralization for a category of remarkably potent antibodies, andatomic-level details for a prefusion-specific antigenic site that shouldserve as a target of improved antibody-based therapies and provide abasis for the development of effective vaccine antigens.

Two human antibodies-D25 and AM22-were determined to be˜50-fold morepotent than palivizumab (FIG. 1A) for neutralizing RSV F, and which alsodo not bind to a soluble form of RSV F stabilized in the postfusionconformation (McLellan et al., J. Virol., 85, 7788 (2011)) (FIG. 1B).D25 and AM22 were previously disclosed (Kwakkenbos et al., Nat. Med.,16, 123 (2010); U.S. Pat. Pub. 2010/0239593; U.S. Pat. Pub.2012/0070446). The lack of D25 and AM22 binding to the postfusion formof RSV F suggested these antibodies might recognize the metastableprefusion conformation.

Structural efforts were focused on the human antibodies, AM22 and D25. A96-well microtiter plate expression format (Pancera et al., PLoS One.2013; 8(2):e55701, 2013, incorporated by reference herein) was used toscreen binding of these antibodies to a panel of RSV F glycoproteinvariants that were captured from cell supernatants on Ni²⁺-NTA ELISAplates. Antibody binding to an F glycoprotein construct (RSV F(+) Fd),comprising RSV F residues 1-513 fused to a C-terminal fibritintrimerization domain was tested (Frank et al., J. Mol. Biol., 308, 1081(2001)). However, complexes were not formed by mixing purified RSV F(+)Fd with purified D25 or AM22 antibody. It was determined thatpurification of the soluble F glycoprotein triggered the metastableprefusion state (Chaiwatpongsakorn et al., J. Virol., 85, 3968 (2011));to overcome this instability, cells expressing RSV F(+) Fd wereincubated with antigen-binding fragments (Fabs) or immunoglobulins (thelatter with an HRV3C protease-cleavage site in the hinge region(McLellan et al., Nature 480, 336, (2011)) in order to trap F in theprefusion state. Alternatively, cells expressing RSV F(+) Fd werecotransfected with separate DNA-expression cassettes encodingantibody-heavy and -light chains (FIG. 5 ). Optimal expression of aD25-F glycoprotein complex was obtained from cotransfection of DNAencoding D25 Fab with DNA encoding RSV F(+) Fd; reasonable complexyields were also observed from the addition of soluble Fab.

Crystallizations were screened for Fab D25 and AM22, alone or in complexwith RSV F(+) Fd. X-ray diffraction data to 1.6 Å resolution wereobtained on hexagonal crystals of Fab D25 by itself, and the structurewas solved by molecular replacement and refined to R_(cryst)/R_(free) of24.5/25.7% (Table 9). Data to 3.6 Å resolution were obtained on cubiccrystals of Fab D25 in complex with RSV F (+) Fd, and this structure wassolved by molecular replacement using the unbound D25 structure andportions of the previously determined postfusion RSV F structure(McLellan et al., J. Virol., 85, 7788 (2011); Swanson et al., Proc.Natl. Acad. Sci. U.S.A., 108, 9619 (2011)) as search models, along withclues from a gold derivative. The structure of the complex was refinedto R_(cryst)/R_(free) of 21.3/26.7% (FIG. 1C) (Table 9).

A complex of one D25 Fab bound to one molecule of the RSV F glycoproteinwas present in the asymmetric unit of the cubic lattice. Three-foldlattice symmetry positioned two other D25-RSV F complexes to generate anextensive RSV F trimeric interface of 2,098 Å². Continuous electrondensity was observed for residues 26 to 513, except for residues 98-136that included the 27 amino-acid fragment removed by proteolytic cleavageof the F₀ precursor to form the F₂ and F₁ subunits (corresponding to N-and C-terminal fragments, respectively) of the mature F glycoprotein.Three sites of N-linked glycosylation were detected in the electrondensity at asparagine residues 27, 70 and 500 (FIG. 2A).

Overall, the D25-bound RSV F structure consists of two lobes packed ateither end of a 7-stranded antiparallel open-ended barrel, two strandsof which (β2 and β7) extend between the two lobes, hydrogen-bonding forover 70 Å and forming integral portions of both lobes and of the centralbarrel. The membrane-proximal lobe, which contains the F₂ N-terminus andF₁ C-terminus, consists of a triple layered β-sandwich and three helices(α8, α9 and α10). Helix α10 forms part of a helix that appeared toextend into the viral membrane and to which the fibrin trimerizationdomain was appended. The membrane-distal lobe, approximately 90 Å fromthe viral membrane, consists of seven helices, packed around athree-stranded antiparallel sheet and a β-hairpin (β3+β4). Extensiveinter-protomer contacts appeared to stabilize the trimeric structure,particularly the hydrophobic N-terminus of the F₁ subunit (also known asthe fusion peptide), which was cradled by the triple β-sandwich from themembrane-proximal lobe of a neighboring protomer. The fusion peptide,contained within the otherwise hollow cavity of the trimer, is connectedto the surface-exposed α2 and α3 helices through a cylindrical openingbetween the protomers that is roughly 10 Å in diameter; this opening maybe used as an exit path for the fusion peptide during triggering.

The structure of the D25-bound F glycoprotein resembled the prefusionstructure of the related parainfluenza virus 5 (PIV5) F glycoprotein(Welch et al., Proc. Natl. Acad. Sci. U.S.A., 109, 16672 (2012); Yin etal., Nature, 439, 38 (2006)) (FIGS. 6 and 7 ). The D25-bound form of RSVF thus appeared to be in the prefusion conformation (FIG. 2 ). To definethe structural rearrangements between pre- and post-fusion F, D25-boundform of RSV F was compared with its postfusion conformation, which wasrecently determined (McLellan et al., J. Virol., 85, 7788 (2011);Swanson et al., Proc. Natl. Acad. Sci. U.S.A., 108, 9619 (2011).

Pre- and post-fusion conformations of RSV F revealed dramatic changes inoverall shape, from a relatively compact oval-shaped structure with aheight of 110 Å to an extended cone approximately 50% longer (170 Å)(FIG. 2A). Despite this remarkable change in conformation, the majorityof the F glycoprotein secondary and tertiary structure was preserved inboth pre- and post-fusion states, with 215 residues showing less than 2Å Cα deviation between the two structures (FIGS. 2A,B). Two regions ofstriking conformational change occur. In the membrane-distal lobe, thefusion peptide and five secondary structure elements (2, α3, β3, β4, andα4) join with the α5-helix to form a single extended postfusion helix(α5_(post)) of over 100 Å in length, which is capped at its N-terminusby the fusion peptide (to aid in clarity, secondary structure elementsof the postfusion structure are labeled with “post” subscript). In themembrane-proximal lobe, the sole parallel strand (β22) of the tripleβ-sandwich—which in the prefusion structure hydrogen bonds toβ1—unravels, allowing the prefusion α10-helix to join with theα5_(post)-helix. Together, the α5_(post) and α10_(post) helicesjuxtapose F, N- and C-termini to form the coiled-coil structurecharacteristic of type I fusion proteins in their postfusionconformation (Colman and Lawrence, Nat. Rev. Mol. Cell Biol., 4, 309(2003)). Overall, portions of the α10 helix move more than 170 Å betweenpre- and post-fusion conformations.

In comparison to the previously reported protease-cleaved, prefusiontype I structures of influenza hemagglutinin (Wilson et al., Nature,289, 366 (1981)), Ebola GP (Lee et al., Nature, 454, 177 (2008)) andPIV5 F(Welch et al., Proc. Natl. Acad. Sci. U.S.A., 109, 16672 (2012)),the location of the RSV fusion peptide is most similar to that ofhemagglutinin (FIG. 7 ), which is surprising given that PIV5 and RSV areboth paramyxoviruses. The RSV F fusion peptide is buried in the centerof the hollow trimer cavity, and is located more than 40 Å away from thelast visible F₂ residue. This suggests that a substantial structuralrearrangement of the fusion peptide occurs after the F₀ precursor iscleaved by the furin-like host protease to produce F₁/F₂. In addition,dramatic structural rearrangements occur between pre- and post-fusionconformations in both the membrane-proximal and membrane-distal lobes,providing insight into the difficulty of stabilizing the prefusionconformation of RSV F. Unlike PIV5 F and human metapneumovirus F, whichcan be stabilized in the prefusion state solely by appending aGCN4-trimerization motif to the C-terminus (Yin et al., Nature, 439, 38(2006); Wen et al., Nat. Struct. Mol. Biol., 19, 461 (2012)), theprefusion RSV F conformation requires stabilization of both themembrane-proximal lobe (accomplished by appending a fibritintrimerization domain (Frank et al., J. Mol. Biol., 308, 1081 (2001)) andthe membrane-distal lobe (which occurs through binding of the D25antibody).

The D25 antibody recognizes the membrane-distal apex of the RSV Fglycoprotein (FIG. 1C). It binds to a quaternary epitope, with theD25-heavy chain interacting with one protomer (involving 638 Å² ofburied interactive-surface area on RSV) and the D25-light chain bindingto both the same protomer (373 Å²) and a neighboring protomer (112 Å²)(FIG. 3A). RSV F contacts are made by 5 of the 6complementarity-determining loops of D25, with the heavy chain 3^(rd)CDR (CDR H3) interacting with the α4-helix (F₁ residues 196-210) andforming intermolecular hydrogen bonds with F₂ residues 63, 65, 66 and 68in the loop between strand β2 and helix α1. While the secondarystructural elements of the D25 epitope remain mostly unchanged, theirrelative orientation changes substantially, with α4-helix pivoting ˜180°relative to strand β2 in pre- and post-fusion conformations (FIG. 3B).This structural rearrangement explains the failure of D25 to bindpostfusion F molecules and suggests D25 inhibits membrane fusion bystabilizing the prefusion conformation of the trimeric F glycoproteincomplex. Although F proteins from human RSV A and B subtypes are highlyrelated in sequence (447/472 or 94.7% of the amino acids comprising themature F2/F₁ ectodomain are identical between known subtypes), sixnaturally observed positions of RSV-sequence variation (residues 67 and74 in F₂, and residues 200, 201, 209, and 213 in F₁) are located in theregion bound by D25 (FIG. 3C). Similarly, of the 56 amino acids inbovine RSV F that are not identical to the mature ectodomain of humanRSV F subtype A, 13 are found in this same region (FIG. 3C). Thus, theD25 epitope, at the apex of the prefusion RSV F structure, may be underimmune pressure and serve as a determinant of subtype-specific immunity(Chambers et al., J. Gen. Virol., 73, 1717 (1992)). For example, basedon sequence analysis, a loop region in F glycoproteins was hypothesizedto exist within the Paramyxoviridae family that might be under immunepressure (Chambers et al., J. Gen. Virol., 73, 1717 (1992)). It has beendemonstrated that binding of RSV sub-group specific monoclonalantibodies can be affected by site-directed mutations between F1residues 200 and 216 (Connor et al., J. Med. Virol., 63, 168 (2001)),and that a peptide comprising F1 residues 205-225 could elicitneutralizing activity in rabbits, although a specific epitope was notdefined (Corvaisier et al., Arch. Virol., 142, 1073 (1997)).

To understand the relationship of the D25 epitope relative to epitopesrecognized by other RSV-neutralizing antibodies, competition for D25binding to RSV-infected cells was tested (FIG. 4A). Notably, AM22competed with D25 for RSV F binding, suggesting that they recognized thesame antigenic site. To further define the site recognized by theseantibodies, negative stain EM on Fab-RSV F complexes was performed. EMimages of Fab D25-RSV F complexes resembled the crystal structure of FabD25-RSV F, and also EM images of Fab AM22-RSV F (FIG. 4B). Together,these results suggested antibodies D25 and AM22 recognize the same or ahighly related antigenic site, which was named “antigenic site 0”.

To characterize antibodies that recognize antigenic site Ø, theirfunctional properties were examined. In addition to their extraordinarypotency and prefusion-specificity (FIG. 1A), all three antibodiesstrongly inhibited fusion when added post-attachment (FIG. 4C), and allthree were unable to block cell-surface attachment (FIG. 4D), suggestingthat the RSV F receptor binds to a region on F not blocked by thesethree antibodies. The receptor-binding domain on the related humanmetapneumovirus F protein is an RGD motif (Cseke et al., Proc. Natl.Acad. Sci. U.S.A., 106, 1566 (2009)) that corresponds to RSV F residues361-363, which reside at the tip of a loop of the central barrel, on theside of the prefusion RSV F trimer not blocked by D25-binding. Althoughthese antibodies do not prevent attachment, the regions of both F₂ andF₁ comprising antigenic site Ø are known to contribute to heparinbinding (Feldman et al., J. Virol., 74, 6442 (2000); Crim et al., J.Virol., 81, 261 (2007)), and it is possible that this region maycontribute to non-specific attachment to heparin sulfate moieties onglycosaminoglycans in concert with the G glycoprotein and other regionsof F. Lastly, AM22 and D25 antibodies neutralized similarly in both Faband immunoglobulin contexts (FIG. 8 ), indicating that avidity did notplay a dominant role as it does for some influenza-virus antibodies(Ekiert et al., Nature, 489, 526 (2012)). Overall, the sharedbinding-specificity and neutralization phenotypes of D25 and AM22 andsuggest that these properties may be characteristic of antibodies thatrecognize antigenic site Ø. By contrast, none of the antibodies thatrecognize other antigenic sites on RSV F associated with neutralizingactivity (sites I, II, and IV) share similar properties of neutralizingpotency and prefusion F specificity (FIGS. 9A-9B).

Despite antigenic site Ø being partially shielded from immunerecognition by multiple mechanisms including conformational masking (itis only present in the metastable prefusion state), quaternary assembly(the site is shared by RSV protomers), antigenic variation (it is one ofthe most variable portions of RSV F), and glycan shielding (the N-linkedglycan attached to Asn70 is at the top of the prefusion F trimer), allthree prefusion-specific antibodies appear to target a similar epitope.The location of antigenic site Ø at the apex of the prefusion F trimershould be readily accessible even on the crowded virion surface, whichmay explain the observation that most neutralizing activity in humansera induced by natural RSV infection is directed against the prefusionform of RSV F (Magro et al., Proc. Natl. Acad. Sci. U.S.A., 109, 3089(2012), although other prefusion-specific antigenic sites cannot beruled out. The high potency of antibodies against antigenic site Øsuggests they could be developed for passive prophylaxis of RSV-induceddisease in neonates. Also, vaccine-based prefusion-specific antibodyelicitation may be assisted by stabilization of the prefusion form ofRSV F, perhaps facilitated by linking mobile and immobile portions ofthe F structure through structure-based design of RSV F variants withdisulfide bonds. It is noted that prefusion-stabilized F contains all ofthe previously characterized neutralizing epitopes as well as antigenicsite Ø. Definition of the D25-RSV F structure thus provides the basisfor multiple new approaches to prevent RSV-induced disease.

Materials and Methods

Viruses and cells. Viral stocks were prepared and maintained aspreviously described (Graham et al., J. Med. Virol., 26, 153 (1988))RSV-expressing Green Fluorescent Protein (GFP) RSV-GFP was constructedas previously reported (Hallak et al., Virology. 271, 264 (2000)). Thetiter of the RSV-GFP stocks used for flow cytometry-based neutralizationand fusion assays was 2.5×10⁷ pfu/ml. The titer of the RSV A2 stock usedfor attachment assay was 1.02×10⁸ pfu/ml. HEp-2 cells were maintained inEagle's minimal essential medium containing 10% fetal bovine serum (10%EMEM) and were supplemented with glutamine, penicillin and streptomycin.

Creation of antibody expression plasmids. DNA encoding antibody heavyand light variable regions were codon-optimized for human expression andsynthesized. AM22 and D25 heavy and light variable regions weresubcloned into pVRC8400 expression plasmids containing in-frame humanconstant domains (IgG1 for heavy chain and kappa for light chain).Variants of the AM22 and D25 heavy chain expression plasmids were madeby inserting either an HRV3C protease site (GLEVLFQGP; SEQ ID NO: 355)or a stop codon into the hinge region.

Expression and purification of antibodies and Fab fragments. Antibodieswere expressed by transient co-transfection of heavy and light chainplasmids into HEK293F cells in suspension at 37° C. for 4-5 days. Thecell supernatants were passed over Protein A agarose, and boundantibodies were washed with PBS and eluted with IgG elution buffer into1/10th volume of 1 M Tris-HCl pH 8.0. AM22 and D25 Fabs were created bydigesting the IgG with Lys-C. The digestion was inhibited by theaddition of Complete protease inhibitor cocktail tablets, and the Faband Fc mixtures was passed back over Protein A agarose to remove Fcfragments. The Fab that flowed through the column was further purifiedby size exclusion chromatography.

RSV neutralization assays. Antibody-mediated neutralization was measuredby a flow cytometry neutralization assay (Chen et al., J. Immunol.Methods, 362, 180 (2010). Briefly, HEp-2 cells were infected withRSV-GFP and infection was monitored as a function of GFP expression at18 hours post-infection by flow cytometry. Data were analyzed by curvefitting and non-linear regression (GraphPad Prism, GraphPad SoftwareInc., San Diego CA).

Postfusion RSV F-binding assay. Purified, soluble RSV F protein in thepostfusion conformation was prepared as described in (McLellan et al.,J. Virol., 85, 7788 (2011). A kinetic ELISA was used to test binding ofmonoclonal antibodies to postfusion RSV F as described previously(McLellan et al., J. Mol. Biol., 409, 853 (2011). Briefly, 96-wellNi²⁺-NTA-coated plates (ThermoFisher Scientific) were coated with 100 μlpostfusion RSV F (1 μg/ml) for one hour at room temperature. 100 μl ofdiluted antibody was added to each well and incubated for one hour atroom temperature. Bound antibodies were detected by incubating theplates with 100 μl HRP-conjugated goat anti-mouse IgG antibody (JacksonImmunoResearch Laboratories, West Grove, PA) or HRP-conjugatedanti-human IgG (Santa Cruz Biolotechnology, Inc, Santa Cruz, CA) for 1hour at room temperature. Then, 100 μl of Super AquaBlue ELISA substrate(eBioscience, San Diego CA) was added to each well and plates were readimmediately using a Dynex Technologies microplate reader at 405 nm(Chantilly, VA). Between steps, plates were washed with PBS-T.

Crystallization and X-ray data collection of unbound D25 Fab.Crystallization conditions were screened using a Cartesian Honeybeecrystallization robot, and initial crystals were grown by the vapordiffusion method in sitting drops at 20° C. by mixing 0.2 μl of D25 Fabwith 0.2 μl of reservoir solution (22% (w/v) PEG 4000, 0.1 M sodiumacetate pH 4.6). Crystals were manually reproduced in hanging drops bycombining protein and reservoir solution at a 2:1 ratio. Crystals wereflash frozen in liquid nitrogen in 27.5% (w/v) PEG 4000, 0.1 M sodiumacetate pH 4.5, and 15% (v/v) 2R,3R-butanediol. X-ray diffraction datato 1.6 Å were collected at a wavelength of 1.00 Å at the SER-CATbeamline ID-22 (Advanced Photon Source, Argonne National Laboratory).

Structure determination and refinement of unbound D25 Fab. X-raydiffraction data were integrated and scaled with the HKL2000 suite(Otwinowski and Minor, in Methods Enzymol. (Academic Press, vol. 276,pp. 307-326, 1997)), and a molecular replacement solution using Igdomains from PDB ID: 3GBM (Ekiert et al., Science, 324, 246 (2009)) and3IDX (Chen et al., Science, 326, 1123 (2009)) as search models wasobtained using PHASER (McCoy et al., J. Appl. Crystallogr., 40, 658(2007)). Manual model building was carried out using COOT (Emsley etal., Acta Crystallogr D Biol Crystallogr, 66, 486 (2010)), andrefinement of individual sites, TLS parameters, and individual B-factorswas performed in PHENIX (Adams et al., Acta Crystallogr D BiolCrystallogr, 66, 213 (2010)). The electron density for the D25 variabledomains was excellent, but the electron density for the constant domainswas poor, possibly a result of flexibility in the elbow angle. Finaldata collection and refinement statistics are presented in Table 8.

Expression and purification of RSV F(+) Fd in complex with D25 Fab. TheRSV F (+) Fd protein construct was derived from the A2 strain (accessionP03420) with three naturally occurring substitutions (P102A, I379V, andM447V) to enhance expression. A mammalian codon-optimized gene encodingRSV F residues 1-513 with a C-terminal T4 fibritin trimerization motif(Frank et al., J. Mol. Biol., 308, 1081 (2001)), thrombin site, 6×His-tag, and StreptagII was synthesized and subcloned into a mammalianexpression vector derived from pLEXm (Aricescu et al., Acta CrystallogrD Biol Crystallogr, 62, 1243 (2006)). Plasmids expressing RSV F(+) Fd,the D25 light chain, and the D25 heavy chain (with or without a stopcodon in the hinge region) were simultaneously transfected into HEK293GnTI^(−/−) cells (Reeves et al., Proc. Natl. Acad. Sci. U.S.A., 99,13419 (2002)) in suspension. Alternatively, just the RSV F(+) Fd plasmidcould be transfected, with purified D25 Fab added to the GnTI^(−/−)cells 3 hours post-transfection. After 4-5 days, the cell supernatantwas harvested, centrifuged, filtered and concentrated. The complex wasinitially purified via Ni²⁺-NTA resin (Qiagen, Valencia, CA) using anelution buffer consisting of 20 mM Tris-HCl pH 7.5, 200 mM NaCl, and 250mM imidazole pH 8.0. The complex was then concentrated and furtherpurified over StrepTactin resin as per the manufacturer's instructions(Novagen, Darmstadt, Germany). After an overnight incubation withthrombin protease (Novagen) to remove the His and Strep tags, an excessof D25 Fab was added to the complex, which was then purified on aSuperose6 gel filtration column (GE Healthcare) with a running buffer of2 mM Tris-HCl pH 7.5, 350 mM NaCl, and 0.02% NaN₃. The eluted complexwas diluted with an equal volume of water and concentrated to −5 mg/ml.Similar procedures were used to express and purify AM22 Fab complexes.

Crystallization and X-ray data collection of RSV F(+) Fd in complex withD25 Fab. Initial crystals were grown by the vapor diffusion method insitting drops at 20° C. by mixing 0.1 μl of RSV F(+) Fd bound to D25 Fabwith 0.1 μl of reservoir solution (40% (w/v) PEG 400, 5% (w/v) PEG 3350,and 0.1 M sodium acetate pH 5.5) (Majeed et al., Structure, 11, 1061(2003)). Crystals were manually reproduced in hanging drops, and thecrystal that diffracted to 3.6 Å was grown using a reservoir solutioncontaining 30% (w/v) PEG 400, 3.75% (w/v) PEG 3350, 0.1 M HEPES pH 7.5,and 1% (v/v) 1,2-butanediol. The crystal was directly transferred fromthe drop into the cryostream, and X-ray diffraction data were collectedremotely at a wavelength of 1.00 Å at the SER-CAT beamline ID-22.

Structure determination and refinement of RSV F(+)Fd in complex with D25Fab. X-ray diffraction data were integrated and scaled with the HKL2000suite (Otwinowski and Minor, in Methods Enzymol. (Academic Press, vol.276, pp. 307-326, 1997)), and a molecular replacement solution wasobtained by PHASER (McCoy et al., J. Appl. Crystallogr., 40, 658 (2007))using the unbound D25 Fab structure and residues 29-42, 49-60, 78-98,219-306, 313-322, 333-343, and 376-459 from the postfusion RSV Fstructure (PDB ID: 3 RRR, McLellan et al., J. Virol., 85, 7788 (2011))as search models. Six sites from a NaAuCl₄ derivative mapped to knownreactive side chains (F residues Met97/His159, Met264/Met274, His317,and Met396; D25 heavy chain residues Met19/His82 and His 59). Manualmodel building was carried out using COOT (Emsley et al., ActaCrystallogr D Biol Crystallogr, 66, 486 (2010)), with secondarystructure elements being built first. Refinement of individual sites,TLS parameters, and individual B-factors was performed in PHENIX (Adamset al., Acta Crystallogr D Biol Crystallogr, 66, 213 (2010)), using theunbound D25 Fab structure, and portions of the postfusion RSV Fstructure as reference models during the refinement. All RSV F residuesin the mature protein were built except for those residues in F₂C-terminal to Met97. Final data collection and refinement statistics arepresented in Table 9.

RSV F competition binding assay. Competition binding of antibodies wasperformed on RSV infected HEp-2 cells. HEp-2 cells were infected with 3MOI (multiplicity of infection) of RSV for 18-20 hours. After infection,cells were separated using cell dissociation solution (Cellstripper,Mediatech Inc., Herndon, VA), and washed with PBS. Cells were seeded at5×10⁴/well in 96-well U-bottom plates in PBS. Monoclonal antibodiesAM22, D25, and 101F were diluted starting at a concentration of 100μg/ml, and added to HEp-2 cells. After 30 minutes 100 ul of Alexa 488conjugated D25 was added at a concentration of 1 μg/ml and incubated at4° C. for one hour. Cells were washed once with PBS, and then fixed with0.5% paraformaldehyde. The binding of D25-Alexa 488 on cells wasmeasured by flow cytomery (LSR II instrument, Becton Dickinson, SanJose, CA). Data were analyzed by using FlowJo software, version 8.5(Tree Star, San Carlos, CA).

Negative staining electron microscopy analysis. Samples were adsorbed tofreshly glow-discharged carbon-coated grids, rinsed shortly with water,and stained with freshly made 0.75% uranyl formate. Images were recordedon an FEI T20 microscope with an Eagle CCD camera. Image analysis and 2Daveraging was performed with Bsoft (Heymann and Belnap, J. Struct.Biol., 157, 3 (2007) and EMAN (Ludtke et al., J. Struct. Biol., 128, 82(1999)).

RSV virus-to-cell fusion inhibition assay. The ability of antibodies toinhibit RSV virus-to-cell fusion was measured as described previously(McLellan et al., J. Virol., 84, 12236 (2010)). Briefly, HEp-2 cellswere seeded in 96-well plates, cultured for 24 hours at 37° C., and thenchilled at 4° C. for one hour prior to assay. RSV-GFP was added topre-chilled cells at 4° C., and then cells were washed in cold PBS toremove unbound virus. Serially-diluted antibodies were added to chilledcells and incubated for 1 hour at 4° C., before transferring to 37° C.for 18 hours. After incubation, cells were trypsinized, fixed in 0.5%paraformaldehyde, and analyzed by flow cytometry to determine thefrequency of GFP-expressing cells.

RSV attachment inhibition assay. The ability of antibodies to inhibitRSV attachment to cells was measured as described previously (McLellanet al., J. Virol., 84, 12236 (2010)). Briefly, HEp-2 cells weredispersed into media, washed with cold PBS, seeded in 96-well v-bottomplates, and chilled for 1 hour at 4° C. before use. Antibodies andheparin, a known RSV attachment inhibitor, were distributed in serialdilutions, then mixed with RSV A2 strain virus for one hour at 37° C.Medium from chilled cells was removed after centrifugation and virus ormixtures of virus and reagents were added to chilled cells and incubatedfor 1 hour at 4° C. After incubation, cells were washed in cold PBS toremove unbound virus, and fixed with 0.5% paraformaldehyde. Virusesbound on cells were detected with FITC-conjugated goat anti-RSVantibody. Cells were washed in cold PBS and evaluated by flow cytometry.Median fluorescence intensities of bound virus were analyzed with FlowJosoftware, version 8.5 (Tree Star, San Carlos, CA).

TABLE 9 Crystallographic data collection and refinement statistics. D25Fab D25 Fab + RSV F Data collection Space group P6₁22 P2₁3 Cellconstants a, b, c (Å) 108.7, 108.7, 139.9 152.3, 152.3, 152.390.0, α, β,γ (°) 90.0, 90.0, 120.0 90.0, 90.0 Wavelength (Å) 1.00 1.00 Resolution(Å) 50.0-1.6 (1.63-1.60) 50.0-3.6 (3.73-3.60) R_(merge) 11.2 (68.0) 12.7(81.4) I/σI 27.3 (2.1) 16.4 (2.0) Completeness (%) 98.3 (86.1) 99.6(99.3) Redundancy 11.0 (5.3) 6.5 (5.2) Refinement Resolution (Å)35.4-1.6 (1.62-1.60) 42.2-3.6 (3.88-3.60) Unique reflections 63,360(2,241) 13,877 (2,742) R_(work)/R_(free) (%) 24.1/25.5 21.3/26.7 No.atoms Protein 3,305 6,778 Ligand/ion 0 0 Water 270 0 B-factors (Å²)Protein 53.0 128.1 Ligand/ion — — Water 44.1 — R.m.s. deviations Bondlengths (Å) 0.007 0.003 Bond angles (°) 1.20 0.91 Ramachandran Favored(%) 96.5 92.0 Allowed (%) 3.0 7.3 Outliers (%) 0.5 0.7

Example 2 Stabilization of RSV F Proteins

This example illustrates design of exemplary RSV F proteins stabilizedin a prefusion conformation. The crystal structure of the RSV F proteinin complex with D25 Fab (i.e., in a prefusion conformation) compared tothe structure of the postfusion RSV F protein (disclosed, e.g., inMcLellan et al., J. Virol., 85, 7788, 2011, with coordinates depositedas PDB Accession No. 3 RRR) shows dramatic structural rearrangementsbetween pre- and post-fusion conformations in both the membrane-proximaland membrane-distal lobes, providing guidance for the stabilization ofthe prefusion conformation of RSV F. Based on a comparison of the pre-and post-fusion RSV F structures, there are two regions that undergolarge conformational changes, located at the N- and C-termini of the F₁subunit. For example, as illustrated in FIG. 2 , the positions 137-216and 461-513 of the F₁ polypeptide undergo structural rearrangementbetween the Pre- and Post-F protein conformations, whereas positions271-460 of the F₁ polypeptide remain relatively unchanged. This exampleillustrates several strategies of stabilizing the RSV F protein in itsprefusion conformation.

To stabilize the N-terminal region of F₁, which is a component ofantigenic site Ø and is involved in binding to antibody D25, variousstrategies have been designed, including introduction of intra-protomerdisulfide bonds, inter-protomer disulfide bonds, cavity filling aminoacid substitutions, repacking substitutions, introduction of N-linkedglycosylation sites, and combinations thereof.

Intra-Protomer Disulfide Bonds

Introduction of two cysteine residues that are within a sufficientlyclose distance to form an intra-protomer disulfide bond in theprefusion, but not postfusion, conformation can lock the F protein inthe prefusion conformation. An intra-molecular disulfide bond can beformed within a single F₂/F_(j) protomer within the trimer, and thuswould not cross-link the three protomers together. Specifically, adisulfide bond formed between a region that changes conformation and aregion that does not change conformation in the pre- and post-fusionstructures should lock the protein in the prefusion conformation. Oneexample is that of the S155C/S290C mutant, where Ser155 is located in aregion that changes conformation, whereas Ser290 is in a region thatdoes not change conformation. Additionally, formation of a disulfidebond between two regions that both change conformation, such as tworesidues located within F₁ positions 137-216, or two residues locatedwithin F₁ positions 461-513, or one residue within F₁ positions 137-216and the second within F₁ positions 461-513, may also be sufficient tolock the protein in the prefusion conformation.

Using the methods described above, several pairs of residues of the RSVF protein were determined to be in close enough proximity in theprefusion conformation, but not the postfusion conformation, to form anintra-protomer disulfide bond if cysteines were introduces at thecorresponding residue pair positions. These residue pairs, as well asthe corresponding amino acid substitutions to SEQ ID NO: 1 needed tointroduce cysteine residues at these positions, are indicated in Table10. Table 10 also lists a SEQ ID NO containing the indicatedsubstitutions, and corresponding to a precursor F₀ construct including asignal peptide, F₂ polypeptide (positions 26-109), pep27 polypeptide(positions 110-136), F₁ polypeptide (positions 137-513), a trimerizationdomain (a Foldon domain) and a thrombin cleavage site (LVPRGS (positions547-552 of SEQ ID NO: 185)) and purification tags (his-tag (HHHHHH(positions 553-558 of SEQ ID NO: 185)) and Strep Tag II (SAWSHPQFEK(positions 559-568 of SEQ ID NO: 185))).

TABLE 10 Exemplary Cross-Linked Cysteine Pairs for Intra-ProtomerDisulfide Bond Stabilization F protein Residue A.A. substitutionsPair(s) for Cysteine corresponding to SEQ ID Substitution SEQ ID NO: 1NO F₁ Substitutions 155 and 290 S155C and S290C 185 151 and 288 G151Cand I288C 189 137 and 337 F137C and T337C 213 397 and 487 T397C andE487C 247 138 and 353 L138C and P353C 257 341 and 352 W341C and F352C267 403 and 420 S403C and T420C 268 319 and 413 S319C and I413C 269 401and 417 D401C and Y417C 270 381 and 388 L381C and N388C 271 320 and 415P320C and S415C 272 319 and 415 S319C and S415C 273 331 and 401 N331Cand D401C 274 320 and 335 P320C and T335C 275 406 and 413 V406C andI413C 277 381 and 391 L381C and Y391C 278 357 and 371 T357C and N371C279 403 and 417 S403C and Y417C 280 321 and 334 L321C and L334C 281 338and 394 D338C and K394C 282 288 and 300 I288C and V300C 284 F₂ and F₁Substitutions 60 and 194 E60C and D194C 190 33 and 469 Y33C and V469C211 54 and 154 T54C and V154C 212 59 and 192 I59C and V192C 246 46 and311 S46C and T311C 276 48 and 308 L48C and V308C 283 30 and 410 E30C andL410C 285

Intermolecular Disulfide Bonds

Introduction of two cysteine residues that are within a sufficientlyclose distance to form an inter-protomer disulfide bond in theprefusion, but not postfusion, conformation can lock the F protein inthe prefusion conformation. An inter-protomer disulfide bond would beformed between adjacent protomers within the trimer, and thus wouldcross-link the three protomers together. Specifically, a disulfide bondformed between a region that changes conformation and a region that doesnot change conformation in the pre- and post-fusion structures shouldlock the protein in the prefusion conformation. One example is that ofthe A153C/K461C mutant, where Ala153 is located in a region that changesconformation, whereas Lys461 is in a region that does not changeconformation. Additionally, formation of a disulfide bond between tworegions that both change conformation, such as two residues locatedwithin F₁ positions 137-216, or two residues located within F₁ positions461-513, or one residue within F₁ positions 137-216 and the secondwithin F₁ positions 461-513, may also be sufficient to lock the proteinin the prefusion conformation.

Using the methods described above, several pairs of residues of the RSVF protein were determined to be in close enough proximity in theprefusion conformation, but not the post-fusion conformation, to form aninter-protomer disulfide bond if cysteines were introduced at thecorresponding residue pair positions. These residue pairs, as well asthe corresponding amino acid substitutions needed to introduce cysteineresidues at these positions, are indicated in Table 11. Table 11 alsolists a SEQ ID NO containing the indicated substitutions, andcorresponding to a precursor F₀ construct also including a signalpeptide, F₂ polypeptide (positions 26-109), pep27 polypeptide (positions110-136), F₁ polypeptide (positions 137-513), a trimerization domain (aFoldon domain) and a thrombin cleavage site (LVPRGS (positions 547-552of SEQ ID NO: 185)) and purification tags (his-tag (HHHHHH (positions553-558 of SEQ ID NO: 185)) and Strep Tag II (SAWSHPQFEK (positions559-568 of SEQ ID NO: 185))).

TABLE 11 Exemplary Cross-Linked Cysteine Pairs for Inter-ProtomerDisulfide Bond Stabilization F protein A.A. substitutions correspondingSEQ ID Residue pair(s) to SEQ ID NO: 1 NO F₁ Substitutions 400 and 489T400C and D489C 201 144 and 406 V144C and V406C 202 153 and 461 A153Cand K461C 205 149 and 458 A149C and Y458C 207 143 and 404 G143C andS404S 209 346 and 454 S346C and N454C 244 399 and 494 K399C and Q494C245 146 and 407 S146C and I407C 264 374 and 454 T374C and N454C 265 369and 455 T369C and T455C 266 402 and 141 V402C and L141C 302 F₂ and F₁Substitutions 74 and 218 A74C and E218C 243

Additionally, multiple stabilizing mutations described herein can becombined to generate a PreF antigen containing more than one stabilizingmutation. Examples of such constructs containing a first and secondresidue pair that form an intra- or an inter-protomer disulfide bond areprovided in Table 12. Table 12 also lists a SEQ ID NO containing theindicated substitutions, and corresponding to a precursor F0 constructalso including a signal peptide, F₂ polypeptide (positions 26-109),pep27 polypeptide (positions 110-136), F₁ polypeptide (positions137-513), a trimerization domain (a Foldon domain) and a thrombincleavage site (LVPRGS (positions 547-552 of SEQ ID NO: 185)) andpurification tags (his-tag (HHHHHH (positions 553-558 of SEQ ID NO:185)) and Strep Tag II (SAWSHPQFEK (positions 559-568 of SEQ ID NO:185))).

TABLE 12 Exemplary Cross-Linked Cysteine Pairs for Combinations ofIntra- and Inter-Protomer Disulfide Bond Stabilization. F proteinSubstitutions corresponding SEQ ID Residue pair(s) to SEQ ID NO: 1 NO155 and 290 (Intra); and S155C and S290C; and 303 402 and 141 (Inter)V402C and L141C 155 and 290(Intra); and S155C and S290C; and 263 74 and218 A74C and E218C

Further, amino acids can be inserted (or deleted) from the F proteinsequence to adjust the alignment of residues in the F protein structure,such that particular residue pairs are within a sufficiently closedistance to form an intra- or inter-protomer disulfide bond in theprefusion, but not postfusion, conformation, which, as discussed above,will stabilize the F protein in the prefusion conformation. Examples ofsuch modification are provided in Table 13. Table 13 also lists a SEQ IDNO containing the indicated substitutions, and corresponding to aprecursor F₆ construct also including a signal peptide, F₂ polypeptide(positions 26-109), pep27 polypeptide (positions 110-136), F polypeptide(positions 137-513), a trimerization domain (a Foldon domain) and athrombin cleavage site (LVPRGS (positions 547-552 of SEQ ID NO: 185))and purification tags (his-tag (HHHHHH (positions 553-558 of SEQ ID NO:185)) and Strep Tag II (SAWSHPQFEK (positions 559-568 of SEQ ID NO:185))),

TABLE 13 Using amino acid insertions to orient F proteins to acceptinter- intra-protomer disulfide bonds, or combinations thereof. Fprotein Substitutions corresponding SEQ ID Residue pair(s) to SEQ ID NO:1 NO 155 and 290 (Intra); and 146 and 460 (Inter); G S155C and S290C;and S146C and N460C; G 258 insertion between position 460/461 insertionbetween position 460/461 155 and 290 (Intra); and 345 and 454(Inter); CS155C and S290C; and N345C and N454G; C 259 insertion between positions453/454 insertion between positions 453/454 155 and 290 (Intra); and 374and 454(Inter); C S155C and S290C; and T374C and N454G; C 260 insertionbetween positions 453/454 insertion between positions 453/454 155 and290 (Intra); and 239 and 279(Inter); C S155C and S290C; and S238G andQ279C; C 261 insertion between positions 238/239 insertion betweenpositions 238/239 155 and 290 (Intra); and 493 paired with C insertionS155C and S290C; and S493C paired with a C 262 between positions 329/330insertion between positions 329/330 183 and 428 (Inter), G insertionbetween positions N183C and N428C; G insertion between positions 296182/183 182/183 183 and 428 (Inter), C insertion between positions N183Cand N427G; C insertion between positions 297 427/428 427/428 155 and 290(Intra); and 183 and 428(Inter); G S155C and S290C; and N183C and N428C;G 298 insertion between positions 182/183 insertion between positions182/183 155 and 290 (Intra); and 183 and 428(Inter); C S155C and S290C;and N183C and N427G; C 299 insertion between positions 427/428 insertionbetween positions 427/428 145 and 460 (Inter), AA insertion betweenpositions S145C and 460C; AA insertion between positions 338 146/147146/147 183 and 423 (Inter), AAA insertion between N183C and K423C; AAAinsertion between 339 positions 182/183 positions 182/183 330 and 430(Inter); CAA insertion between A329C and S430C; and a CAA insertionbetween 340 positions 329/330 positions 329/330

Cavity-Filling Substitutions

Comparison of the crystal structure of the RSV F protein in complex withD25 Fab (i.e., in a prefusion conformation) compared to the structure ofthe postfusion RSV F protein (disclosed, e.g., in

McLellan et al., J. Virol., 85, 7788, 2011; structural coordinates ofthe RSV F protein in its postfusion conformation are deposited in theProtein Data Bank (PDB) as PDB Accession No. 3 RRR) identifies severalinternal cavities or pockets in the prefusion conformation that mustcollapse for F to transition to the postfusion conformation. Thesecavities are listed in Table 14. Accordingly, filling these internalcavities stabilizes F in the prefusion state, by preventing transitionto the postfusion conformation. Cavities are filled by substitutingamino acids with large side chains for those with small sidechains. Thecavities can be intra-protomer cavities, or inter-protomer cavities. Oneexample of a RSV F cavity-filling modification to stabilize the RSVprotein in its prefusion conformation is the S190F/V207L mutant.

Using this strategy, several cavity filling modifications wereidentified to stabilize the RSV F protein in its prefusion conformation.These modifications, are indicated in Table 14. Table 14 also lists aSEQ ID NO containing the indicated substitutions, and corresponding to aprecursor F₀ construct including a signal peptide, F₂ polypeptide(positions 26-109), pep27 polypeptide (positions 110-136), F₁polypeptide (positions 137-513), a trimerization domain (a Foldondomain) and a thrombin cleavage site (LVPRGS (positions 547-552 of SEQID NO: 185)) and purification tags (his-tag (HHHHHH (positions 553-558of SEQ ID NO: 185)) and Strep Tag II (SAWSHPQFEK (positions 559-568 ofSEQ ID NO: 185))).

TABLE 14 Exemplarity cavity-filling amino acid substitution Cavity A.A.Substitutions SEQ ID NO: Ser190 and Val207 190F and 207L 191 Val207 207Land 220L 193 Ser190 and Val296 296F and 190F 196 Ala153 and Val207 220Fand 153W 197 Val207 203W 248 Ser190 and Val207 83W and 260W 192 Val29658W and 298F 195 Val90 87F and 90F 194

The indicated cavities are referred to by a small residue abutting thecavity that can be mutated to a larger residue to fill the cavity. Itwill be understood that other residues (besides the one the cavity isnamed after) could also be mutated to fill the same cavity.

Repacking Substitutions

Additionally, the prefusion conformation of the RSV F protein may bestabilized by increasing the interactions of neighboring residues, suchas by enhancing hydrophobic interactions or hydrogen-bond formation.Further, the prefusion conformation of the RSV F protein may bestabilized by reducing unfavorable or repulsive interactions ofneighboring residues that lead to metastability of the prefusionconformation. This can be accomplished by eliminating clusters ofsimilarly charged residues. Examples of such modifications are indicatedin Table 15. Table 15 also lists a SEQ ID NO containing the indicatedsubstitutions, and corresponding to a precursor F₀ construct including asignal peptide, F₂ polypeptide (positions 26-109), pep27 polypeptide(positions 110-136), F₁ polypeptide (positions 137-513), a trimerizationdomain (a Foldon domain) and a thrombin cleavage site (LVPRGS (positions547-552 of SEQ ID NO: 185)) and purification tags (his-tag (HHHHHH(positions 553-558 of SEQ ID NO: 185)) and Strep Tag II (SAWSHPQFEK(positions 559-568 of SEQ ID NO: 185))).

TABLE 15 Repacking Amino Acid Substitutions Substitutions SEQ ID NOI64L, I79V, Y86W, L193V, L195F, Y198F, I199F, L203F, V207L, I214L 227I64L, I79L, Y86W, L193V, L195F, Y198F, I199F, L203F, I214L 228 I64W,I79V, Y86W, L193V, L195F, Y198F, I199F, L203F, V207L, I214L 229 I79V,Y86F, L193V, L195F, Y198F, I199F, L203F, V207L, I214L 230 I64V, I79V,Y86W, L193V, L195F, Y198F, I199Y, L203F, V207L, I214L 231 I64F, I79V,Y86W, L193V, L195F, Y198F, I199F, L203F, V207L, I214L 232 I64L, I79V,Y86W, L193V, L195F, I199F, L203F, V207L, I214L 233 V56I, T58I, V164I,L171I, V179L, L181F, V187I, I291V, V296I, A298I 234 V56I, T58I, V164I,V179L, T189F, I291V, V296I, A298I 235 V56L, T58I, L158W, V164L, I167V,L171I, V179L, L181F, V187I, I291V, V296L 236 V56L, T58I, L158Y, V164L,I167V, V187I, T189F, I291V, V296L 237 V56I, T58W, V164I, I167F, L171I,V179L, L181V, V187I, I291V, V296I 238 V56I, T58I, I64L, I79V, Y86W,V164I, V179L, T189F, L193V, L195F, Y198F, I199F, L203F, 239 V207L,I214L, I291V, V296I, A298I V56I, T58I, I79V, Y86F, V164I, V179L, T189F,L193V, L195F, Y198F, I199F, L203F, V207L, 240 I214L, I291V, V296I, A298IV56I, T58W, I64L, I79V, Y86W, V164I, I167F, L171I, V179L, L181V, V187I,L193V, L195F, 241 Y198F, I199F, L203F, V207L, I214L, I291V, V296I V56I,T58W, I79V, Y86F, V164I, I167F, L171I, V179L, L181V, V187I, L193V,L195F, Y198F, 242 I199F, L203F, V207L, I214L, I291V, V296I D486N, E487Q,D489N, and S491A 249 D486H, E487Q, and D489H 250 T400V, D486L, E487L,and D489L 251 T400V, D486I, E487L, and D489I, 252 T400V, S485I, D486L,E487L, D489L, Q494L, and K498L 253 T400V, S485I, D486I, E487L, D489I,Q494L, and K498L 254 K399I, T400V, S485I, D486L, E487L, D489L, Q494L,E497L, and K498L 255 K399I, T400V, S485I, D486I, E487L, D489I, Q494L,E497L, and K498L 256 L375W, Y391F, and K394M 286 L375W, Y391F, and K394W287 L375W, Y391F, K394M, D486N, E487Q, D489N, and S491A 288 L375W,Y391F, K394M, D486H, E487Q, and D489H 289 L375W, Y391F, K394W, D486N,E487Q, D489N, and S491A 290 L375W, Y391F, K394W, D486H, E487Q, and D489H291 L375W, Y391F, K394M, T400V, D486L, E487L, D489L, Q494L, and K498M292 L375W, Y391F, K394M, T400V, D486I, E487L, D489I, Q494L, and K498M293 L375W, Y391F, K394W, T400V, D486L, E487L, D489L, Q494L, and K498M294 L375W, Y391F, K394W, T400V, D486I, E487L, D489I, Q494L, and K498M295 F137W and R339M 326 F137W and F140W 327 F137W, F140W, and F488W 328D486N, E487Q, D489N, S491 A, and F488W 329 D486H, E487Q, D489H, andF488W 330 T400V, D486L, E487L, D489L, and F488W 331 T400V, D486I, E487L,D489I, and F488W 332 D486N, E487Q, D489N, S491A, F137W, and F140W 333D486H, E487Q, D489H, F137W, and F140W 334 T400V, D486L, E487L, D489L,F137W, and F140W 335 L375W, Y391F, K394M, F137W, and F140W or 336 L375W,Y391F, K394M, F137W, F140W, and R339M 337

Glycosylation Mutations

Additionally, introduction of N-linked glycosylation sites that would besolvent-accessible in the prefusion RSV F conformation butsolvent-inaccessible in the postfusion RSV F conformation may stabilizeRSV F in the prefusion state by preventing adoption of the postfusionstate. To create an N-linked glycosylation site, the sequenceAsn-X-Ser/Thr (where X is any amino acid except Pro) may be introduced.This can be accomplished by substitution of a Ser/Thr amino acid tworesidues C-terminal to a native Asn residue, or by substitution of anAsn amino acid two residues N-terminal to a native Ser/Thr residue, orby substitution of both an Asn and Ser/Thr residue separated by onenon-proline amino acid.

Using this strategy, several locations for N-linked glycosylation sitesthat would be solvent-accessible in the prefusion RSV F conformation butsolvent-inaccessible in the postfusion RSV F conformation wereidentified. These modifications are indicated in Table 16. Table 16 alsolists the SEQ ID NO containing the indicated substitutions, andcorresponding to a precursor F₀ construct including a signal peptide, F₂polypeptide (positions 26-109), pep27 polypeptide (positions 110-136),F₁ polypeptide (positions 137-513), a trimerization domain (a Foldondomain) and a thrombin cleavage site (LVPRGS (positions 547-552 of SEQID NO: 185)) and purification tags (his-tag (HHHHHH (positions 553-558of SEQ ID NO: 185)) and Strep Tag II (SAWSHPQFEK (positions 559-568 ofSEQ ID NO: 185))).

TABLE 16 Exemplary N-linked glycosylation N-linked glycosylationExemplary SEQ position Exemplary substitutions ID NO 506 I506N and K508T198 175 A177S 199 178 V178N 200 276 V278T 203 476 Y478T 204 185 V185Nand V187T 214 160 L160N and G162S 215 503 L503N and a F505S 216 157V157N 217

Example 3 Stabilizing the Membrane Proximal Lobe of PreF Antigens

As discussed above, the crystal structure of the RSV F protein incomplex with D25 Fab (i.e., in a prefusion conformation) compared to thestructure of the postfusion RSV F protein ((disclosed, e.g., in McLellanet al., J. Virol., 85, 7788, 2011, with coordinates deposited as PDBAccession No. 3 RRR)) shows dramatic structural rearrangements betweenpre- and post-fusion conformations in the membrane-distal lobe. Based ona comparison of the pre- and post-fusion RSV F structures, there are tworegions that undergo large conformational changes, located at the N- andC-termini of the F₁ subunit. For example, as illustrated in FIG. 2 , thepositions 137-216 and 461-513 of the F₁ polypeptide undergo structuralrearrangement between the Pre- and Post-F protein conformations, whereaspositions 271-460 of the F₁ polypeptide remain relatively unchanged.This example illustrates several strategies of stabilizing theC-terminal region of F₁, which includes the membrane proximal lobe ofthe RSV F protein. Various strategies have been identified, includingintroduction of a trimerization domain (as discussed above),introduction of cysteine pairs that can form a disulfide bond thatstabilizes the C-terminal region of F1, and introduction of atransmembrane domain (e.g., for applications including a membrane-boundPreF antigen).

Disulfide Bonds

One strategy for stabilizing the membrane proximal lobe of the F proteinis to introduce one or more cysteine substitutions that introduce adisulfide bond that that stabilizes the C-terminal portion of F₁ (forexample, for an application including a soluble PreF antigen). Such astrategy can be combined with any of the stabilization modificationsprovided herein, for example, those described in Example 2, such as a F₁protein with a S155C/S290C cysteine substitution. One strategy includesintroduction of two cysteine residues that are within a sufficientlyclose distance to form an inter-protomer disulfide bond that links theC-terminal region of the F, protein in the prefusion conformation. Aninter-protomer disulfide bond would be formed between adjacent protomerswithin the trimer, and thus would cross-link the three protomerstogether. Using the methods described above, several pairs of residuesof the RSV F protein were determined to be in close enough proximity inthe prefusion conformation, to form an inter-protomer disulfide bond ifcysteines were introduces at the corresponding residue pair positions.

Examples of cysteine substitutions that can be introduced to generate adisulfide bond that stabilizes the membrane proximal lobe includecysteine substitutions at residue pairs:

-   -   (a) 486 and 487    -   (b) 486 and 487; with a P insertion between positions 486/487    -   (c) 512 and 513    -   (d) 493; C insertion between 329/330    -   (e) 493; C insertion between 329/330, and G insertion between        492/493

Further, the length of the F₁ polypeptide can be varied, depending onthe position of the of the C-terminal cysteine pair. For example, the F₁polypeptide can include positions 137-481, which eliminate the α10 helixfrom the F₁ polypeptide.

Examples of constructs containing modifications including cysteines atthese residue pairs, as well as additional description are listed inTable 17. Table 17 also lists a SEQ ID NO containing the indicatedsubstitutions, and corresponding to a precursor F₀ construct alsoincluding a signal peptide, F₂ polypeptide (positions 26-109), pep27polypeptide (positions 110-136), F₁ polypeptide (with varyingpositions).

TABLE 17 Disulfide bonds to stabilize the membrane proximal lobe of Fprotein. Substitutions/insertion Description F₁ positions SEQ ID NOD486C/E487C; The D486C and E487C mutant allows inter-protomer disulfidebond 137-481 304 S155C/S290C formation while the S155C/S290C mutationsstabilize the prefusion format, this construct does not have a Foldon oralpha-10 helix. S155C/S290C; The D486C and E487C mutant should allowinter-protomer disulfide 137-481 305 D486C/E487C; P bond formation whilethe S155C/S290C mutations stabilize the insertion between prefusionformat, this construct does not have a Foldon or alpha-10 positions486/487 helix. N183C/N428C; The D486C and E487C mutant should allowinter-protomer disulfide 137-481 306 D486C/E487C; G bond formation whilethe 183C and 428C mutations stabilize the insertion between 182/183prefusion format. This construct removes the Foldon sequence and thealpha-10 sequence. N183C/K427G; C The D486C and E487C mutant shouldallow inter-protomer disulfide 137-481 307 insertion between bondformation while the 183C and 428C mutations stabilize the 247/428;D486C/E487C prefusion format. This construct removes the Foldon sequenceand the P; insertion between alpha-10 sequence. positions 486/487V402C/L141C; The 141C and 402C stabilize the prefusion form by lockingdown the  1-513 308 L512C/L513C fusion peptide. While the 512C and 513Ccreate an inter-protomer disulfide bond; this construct does not have afoldon domain. S155C/S290C; The 141C and 402C stabilize the prefusionform by locking down the  1-513 309 V402C/L141C fusion peptide inconjunction with the S155C/S290C. While the 512C L512C/L513C and 513Ccreate an inter-protomer disulfide bond, the foldon sequence is removed.S155C/S290C; Removal of the “foldon” and the facilitation ofintermolecular disulfide 137-491 310 S493C; C insertion bondstabilization while the S155C/S290C mutations stabilize the between329/330 prefusion format S155C/S290C; Removal of the “foldon” and thefacilitation of intermolecular disulfide 137-491 311 S493C; C insertionbond stabilization while the S155C/S290C mutations stabilize the between329/330; prefusion format G insertion between 492/493

Transmembrane Domains

Another strategy for stabilizing the membrane proximal lobe of the Fprotein is to include a transmembrane domain on the F₁ protein, forexample, for an application including a membrane anchored PreF antigen.For example, the presence of the transmembrane sequences is useful forexpression as a transmembrane protein for membrane vesicle preparation.The transmembrane domain can be linked to a F₁ protein containing any ofthe stabilizing mutations provided herein, for example, those describedin Example 2, such as a F₁ protein with a S155C/S290C cysteinesubstitution. Additionally, the transmembrane domain can be furtherlinked to a RSV F₁ cytosolic tail. Examples of precursor F₀ constructsincluding a signal peptide, F₂ polypeptide (positions 26-109), pep27polypeptide (positions 110-136), F₁ polypeptide (positions 137-513), aRSV transmembrane domain are provided as SEQ ID NOs: 323 (without acytosolic domain) and 324 (with a cytosolic domain).

Example 4 Single Chain PreF Antigens

This example illustrates recombinant RSV F proteins that lack the nativefurin cleavage sites, such that the F protein protomer is formed as asingle polypeptide chain, instead of a F₂/F₁ heterodimer.

Table 18 lists several single chain PreF antigens that include deletionof F positions 98-149, which removes the two furin cleavage sites, thepep27 polypeptide, and the fusion peptide. The remaining portions of theF₁ and F₂ polypeptides are joined by a linker. Additionally, severalstrategies can be employed to stabilize the single chain constructs in aprefusion conformation, including use of the strategies described inexamples 2 and 3, above. Table 18 also lists a SEQ ID NO containing theindicated substitutions, and corresponding to a precursor F₀ constructalso including a signal peptide, F₂ polypeptide (positions 26-109),pep27 polypeptide (positions 110-136), F₁ polypeptide (with varyingpositions).

TABLE 18 Single chain PreF antigens C-term SEQ ID SubstitutionsDiscussion F2/F1 Linker Stabilization NO S155C/S290C(A) The rationale for this construct is GSGNVGLGG Foldon 313 L373Rto create a single chain RSV fusion (SEQ ID NO: 356) Δ98-149molecule, remove the nucleus locali-zation signal (L373R), and the fusion peptide (, while the S155C/S290Cmutations stabilize the prefusion format S155C/S290C Same as (A)GSGNWGLGG Foldon 314 L373R (SEQ ID NO: 357) Δ98-149 S155C/S290CSame as (A) GSGNIGLGG Foldon 315 L373R (SEQ ID NO: 358) Δ98-149S155C/S290C Same as (A) GSGGNGIGLGG Foldon 316 L373R (SEQ ID NO: 359)Δ98-149 S155C/S290C Same as (A) GSGGSGGSGG Foldon 317 L373R(SEQ ID NO: 360) Δ98-149 S155C/S290C Same as (A) GSGNVLGG Foldon 318L373R (SEQ ID NO: 361) Δ98-149 S155C/S290C(B) The rationale for this construct is GSGNVGLGG D486C/E487C; 319 L373Rto create a single chain RSV fusion (SEQ ID NO: 362) P insertion Δ98-149molecule, remove the nucleus locali- betweenzation signal, and the fusion peptide positionsand also the alpha 10 helix and Foldon, 486/487while the S155C/S290C mutations stabilize the prefusion formatS155C/S290C/ Same as (B) GSGNVGLGG L512C/L513C 320 L373R(SEQ ID NO: 363) Δ98-149 S155C/S290CL Same as (A) GSGNIGLGG TM 322 373R(SEQ ID NO: 364) Δ98-149

Example 5 RSV F Protein Stabilized with a Disulfide Bond and aTrimerization Domain

This example illustrates production of a RSV F protein stabilized with adisulfide bond and a trimerization domain. As illustrated in FIG. 10 ,the serine residues at positions 155 and 290 (indicated by arrows andred highlighting in the ribbon diagrams) are adjacent to each other inthe prefusion conformation of RSV F protein, but not in the post fusionconformation of the RSV F protein. Further, the side chains of theseresidues are oriented towards one another. However, the side chains ofthe residues adjacent to serine 155, valine 154 and lysine 156, areoriented away from the side chain of serine 290. In view of thesefindings, a recombinant RSV F protein was constructed with S155C andS290C substitutions. It was expected that the cysteine residues in this155/290 construct would form a disulfide bond that would lock therecombinant RSV F protein in the prefusion conformation, but thatincorporation of cysteines at positions 154 or 156 (instead of position155) would fail to produce a stabilizing disulfide bond.

A nucleic acid molecule encoding a native RSV F₀ polypeptide was mutatedusing standard molecular biology techniques to encode the RSV F proteincalled RSVF(+)FdTHS S155C, S290C, and set forth as SEQ ID NO: 185:

(SEQ ID NO: 185) MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALRTGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLLMQSTPATNNRARRELPRFMNYTLNNAKKTNVTLSKKRKRRFLGFLLGVGSA IASGVAV CKVLHLEGEVNKIKSALLSTNKAVVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQKNNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLMSNNVQIVRQQSYSIM C IIKEEVLAYVVQLPLYGVIDTPCWKLHTSPLCTTNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTMNSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGKTKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKSLYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELL SAIGGYIPEAPRDGQAYVRKDGEWVL LSTFLGGLVPRGSHHHHHHSAWSHPQFEK.

RSVF(+)FdTHS S155C, S290C includes a signal peptide (residues 1-25), F₂polypeptide (residues 26-109), Pep27 polypeptide (residues (110-136), F₁polypeptide (residues 137-513), Foldon domain (residues 514-544), and athrombin cleavage site (LVPRGS (positions 547-552 of SEQ ID NO: 185))and purification tags (his-tag (HHHHHH (positions 553-558 of SEQ ID NO:185)) and Strep Tag II (SAWSHPQFEK (positions 559-568 of SEQ ID NO:185))). Control constructs were also generated with V154C or K156Csubstitutions instead of the S155C substitution.

When expressed in cells, RSVF(+)FdTHS S155C, S290C was processed andexpressed as a stable and soluble RSV F protein; however, the controlconstructs with 154/290 or 156/290 substitutions failed to express(likely because they failed to fold in a soluble conformation) (see FIG.10 ).

The RSVF(+)FdTHS S155C, S290C construct was purified and tested forantibody binding to the prefusion specific antibodies AM22 and D25, aswell as 131-2a antibody (which binds antigenic site I, present on pre-and post-fusion RSV F conformations), motavizumab and palivizumab (whichbind antigenic site II, present on pre- and post-fusion RSV Fconformations), and 101F antibody (which binds antigenic site IV,present on pre- and post-fusion RSV F conformations). As shown in FIG.11 (left graph), all of these antibodies specifically bound to thepurified RSVF(+)FdTHS S155C, S290C construct, indicating thatRSVF(+)FdTHS S155C, S290C maintains a prefusion conformation. Theresults further indicate that this construct maintains antigenic sitesI, II and IV, common to both the pre- and post-fusion conformations ofRSV F.

To demonstrate that purified RSVF(+)FdTHS S155C, S290C is in a trimericconformation, this construct was passed over a size-exclusionchromatography column. As shown in FIG. 11 (right graphs) a preparationof purified RSVF(+)FdTHS S155C, S290C eluted in a single peakcorresponding to the molecular weight of the trimeric F protein. Incontrast, a preparation of a control construct lacking the S155C andS290C substitutions, which is not expected to be stabilized in theprefusion conformation, eluted in multiple peaks, indicating thepresence of rosettes of triggered F protein and aggregates, indicatingthat this control construct is not stable in a homogeneous prefusionconformation.

To further confirm that the RSVF(+)FdTHS S155C, S290C construct isstabilized in a prefusion conformation, electron microscopy studies wereperformed (FIG. 12 ) and demonstrate that RSVF(+)FdTHS S155C, S290C formhomogeneous population of structures with a shape similar to that of theprefusion conformation of RSV F, and significantly different from thatof the postfusion F protein (right image, from Martin et al., J. Gen.Virol., 2006).

Crystallography studies were performed to demonstrate that purifiedRSVF(+)FdTHS S155C, S290C is homogeneous in solution. Formation ofcrystals in aqueous solution is a stringent test for the homogeneity ofa protein in solution. FIG. 15 shows pictures of the crystals formed bypurified RSVF(+)FdTHS S155C, S290C in aqueous buffer containing 0.2 Mlithium sulfate, 1.64 M Na/K tartrate and 0.1 M CHES, at pH 9.5. Theformation of RSVF(+)FdTHS S155C, S290C crystals in aqueous bufferdemonstrates that this protein is substantially homogeneous in solution.

Example 6 Induction of a Neutralizing Immune Response Using a PreFAntigen

This example illustrates use of a PreF antigen to elicit a RSVneutralizing immune response in a subject.

Eight week old pathogen-free CB6F1/J mice (Jackson Labs) were dividedinto 5 groups of 10 each, and immunized with the following regimens:

-   -   1) live RSV A2 (RSV) at 5×10⁶ pfu intranasally;    -   2) formalin-inactivated alum-precipitated RSV(FI-RSV)        intramuscularly (IM);    -   3) stabilized prefusion RSV F (RSVF(+)FdTHS S155C, S290C;        prefusion F) 20 μg in polyL:C 50 μg IM;    -   4) postfusion RSV F trimer ((postfusion RSV) 20 μg in polyL:C 50        μg IM; and

Group 1 (live RSV) was infected once at time 0, and all other groupswere immunized at 0 and 3 weeks. Serum was obtained at week 5, two weeksafter the 2^(nd) IM injection or five weeks post RSV infection.Neutralizing activity was determined by the following method: Sera weredistributed as four-fold dilutions from 1:10 to 1:40960, mixed with anequal volume of recombinant mKate-RSV expressing prototypic F genes fromeither strain A2 (subtype A) or 18537 (subtype B) and the Katushkafluorescent protein, and incubated at 37′C for one hour. Next, 50 μl ofeach serum dilution/virus mixture was added to HEp-2 cells that had beenseeded at a density of 1.5×10⁴ in 30 μl MEM (minimal essential medium)in each well of 384-well black optical bottom plates, and incubated for20-22 hours before spectrophotometric analysis at Ex 588 nm and Em 635nm (SpectraMax Paradigm, Molecular Devices, Sunnyvale, CA 94089). TheIC50 for each sample was calculated by curve fitting and non-linearregression using GraphPad Prism (GraphPad Software Inc., San Diego CA).P values were determined by Student's T-test. The above method formeasuring RSV neutralization was performed substantially as describedpreviously (see, e.g., Chen et al. J. Immunol. Methods., 362:180-184,2010, incorporated by reference herein), except that the readout was bya fluorescent plate-reader instead of flow cytometry.

Using this assay, generally antibody responses above ˜100 EC₅₀ would beconsidered to be protective. As shown in FIGS. 13 and 14 , miceadministered an RSV F protein stabilized in a prefusion conformation(RSV F (RSVF(+)FdTHS S155C, S290C) produced a neutralizing immuneresponse to RSV A ˜15-fold greater than that produced by miceadministered a RSV F protein in a postfusion conformation, and aresponse to RSV B ˜5-fold greater than that produced by miceadministered a RSV F protein in a postfusion conformation. FIG. 13 showsthe results after 5 weeks post-initial immunization, and FIG. 14 showsresults after 7 weeks post immunization. The mean elicited IC50 valuesare also shown in FIGS. 13 and 14 . The difference in neutralizationbetween RSV A and B subgroups is not surprising as the RSVF(+)FdTHSS155C, S290C construct is derived from a F protein from an RSV Asubgroup. It is expected that immunization with a correspondingconstruct derived from a RSV B strain would generate neutralizing seramore specific for RSV B (see FIG. 41 ).

Further, it was shown that the stabilized prefusion F can be formulatedin alum as well as polyL:C and retain immunogenicity conferred byantibody responses to antigenic site Ø. BALB/c mice were immunized with20 μg of the DS S155C/S290C version of stabilized prefusion F derivedfrom subtype A and formulated with alum (aluminum hydroxide gel 10mg/ml, Brenntag, Frederikssund, Denmark) or polyL:C. Mice wereinoculated at 0 and 3 weeks, and at the 5 week time point (2 weeks afterthe second injection), serum was obtained for neutralization assays (seeFIG. 42 ). The results show that immunization with a RSV F proteinstabilized in a prefusion conformation produces a protective immuneresponse to RSV.

Example 7 Treatment of Subjects with the Disclosed Antigens

This example describes methods that can be used to treat a subject thathas or is at risk of having an RSV infection by administration of one ormore of the disclosed PreF antigens, or a nucleic acid or a viral vectorencoding, expressing or including a PreF antigen. In particularexamples, the method includes screening a subject having, thought tohave, or at risk of having (for example due to impaired immunity,physiological status, or exposure to RSV) an RSV infection. Subjects ofan unknown infection status can be examined to determine if they have aninfection, for example using serological tests, physical examination,enzyme-linked immunosorbent assay (ELISA), radiological screening orother diagnostic technique known to those of ordinary skill in the art.In some examples, a subject is selected that has an RSV infection or isat risk of acquiring an RSV infection. Subjects found to (or known to)have an RSV infection and thereby treatable by administration of thedisclosed PreF antigens, or a nucleic acid or a viral vector encoding,expressing or including a PreF antigen are selected to receive the PreFantigens, or a nucleic acid or a viral vector encoding, expressing orincluding a PreF antigen. Subjects may also be selected who are at riskof developing an RSV infection for example, the elderly, theimmunocompromised and the very young, such as infants.

Subjects selected for treatment can be administered a therapeutic amountof disclosed PreF antigens. An immunogenic composition including thePreF antigen can be administered at doses of 0.1 μg/kg body weight toabout 1 mg/kg body weight per dose, such as 0.1 μg/kg body weight toabout 1 μg/kg body weight, 0.1 μg/kg body weight to about 10 μg/kg bodyweight per dose, 1 μg/kg body weight-100 μg/kg body weight per dose, 100μg/kg body weight-500 μg/kg body weight per dose, or 500 μg/kg bodyweight-1000 μg/kg body weight per dose or even greater. In someembodiments, about 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or about 100μg of the PreF antigen is included in the immunogenic composition thatis administered to the subject in a single dose. The immunogeniccomposition can be administered in several doses, for examplecontinuously, daily, weekly, or monthly. The mode of administration canbe any used in the art, such as nasal administration. The amount ofagent administered to the subject can be determined by a clinician, andmay depend on the particular subject treated. Specific exemplary amountsare provided herein (but the disclosure is not limited to such doses).

Example 8 RSV F Protein Stabilized with a Disulfide Bond, Cavity FillingSubstitutions, and a Trimerization Domain

This example illustrates production of a RSV F protein stabilized with adisulfide bond and a trimerization domain.

FIG. 16 shows the design of a recombinant RSV F protein stabilized byengineered disulfide bond mutations S155C and S290C (termed “DS”),cavity-filling mutations S190F and V207L (termed “Cav1”), and aheterologous trimerization domain appended to the C-terminus of the F1polypeptide of the F protein. The three-dimensional structure depictedis the D25-bound RSV F structure, and is shown with two of the protomersdisplayed as a molecular surface colored pink and tan, and the thirdprotomer displayed as ribbons. The N- and C-terminal residues of F₁ thatmove more than 5 Å between the pre and postfusion conformations areshown. Insets show the engineered disulfide bond between residues S155Cand S290C, as well as the space-filling cavity mutations S190F andV207L. A model of the T4 phage fibritin trimerization domain is shown atthe base of the prefusion trimer.

A RSV F protein including the S155C, S290C, S190F and V207L (Cav1)substitutions in human RSV subtype A, and the appended C-terminalheterologous foldon domain, was expressed and purified using methodsdescribed in Example 1 and 5, and is termed RSV_A F(+)FdTHS DSCav1.

The antigenic characterization of RSV_A F(+)FdTHS DSCav1 are shown inFIG. 17 . The association and dissociation rates of soluble D25, AM22,5C4, 101F, Motavizumab, and Palivizumab Fab with immobilized RSV_AF(+)FdTHS DSCav1 were measured using an OctetRED 384™ instrument(ForteBio, Melno Park, CA). Equilibrium dissociation constants for eachantibody are provided.

The purity of RSV_A F(+)FdTHS DSCav1 is illustrated by size exclusionchromatography (FIG. 18 ). Purified protein, after thrombin cleavage toremove the tags, was passed over a 16/70 Superose 6 size exclusioncolumn. The elution volume is consistent with a glycosylated trimer.

The antigenic and physical characteristics, including yield fromtransiently expressed plasmids, antigenicity against various antigenicsites, and the retention of D25-binding (provided as a fractionalamount) after 1 hour of incubation at various temperatures (350 mM NaClpH 7.0, at 50° C., 70° C., or 90° C.), pHs (350 mM NaCl pH 3.5 or pH 10,at 25° C.), and osmolality (10 mM or 3000 mM osmolarity, pH 7.0, at 25°C.), or to 10 cycles of freeze-thaw (in 350 mM NaCl pH 7.0), of RSV_AF(+)FdTHS variants stabilized by DS, Cav1 or DSCav1 mutations are shownin FIG. 19 . The DSCav1 variant retains antigenic site Ø recognition,with improved physical stability, as judged by higher retention ofD25-reactivity after exposure to extremes of temperature, pH, osmolalityand freeze-thaw, then either DS or Cav1 variants.

To investigate the structural properties of the DSCav1 mutant, the threedimensional structure of RSV_A F(+)FdTHS DSCav1 was determined usingX-ray crystallography. FIG. 20 shows a ribbon representation of the 3.1Å crystal structure of RSV_A F(+)FdTHS DSCav1. Warmer colors and thickerribbons correspond to increasing B-factors. Despite stabilizingmutations, antigenic site Ø, at the trimer apex, retains significantflexibility. FIG. 21 shows comparison of the structure of RSV_AF(+)FdTHS DSCav1 to the structure of D25-bound RSV F. FIG. 22 highlightsthe stabilizing mutations in RSV_A F(+)FdTHS DSCav1 structure. Observedelectron density corresponding to the disulfide bond between cysteineresidues 155 and 290 (left), as well as the cavity-filling Phe190residue (right), indicates that these modifications are present in thecrystal.

To determine the immunogenicity of the RSV_A F(+)FdTHS DSCav1 construct,mice and non-human primates were inoculated with this construct and seraobtained from the inoculated animals was tested for neutralization ofRSV (FIGS. 23 and 24 ). Mice were immunized, and the neutralizationactivity of the resulting sera was tested, as described in Example 6,above. Briefly, ten CB6 mice per group were immunized with 10 μg of theindicated RSV F protein mixed with 50 μg of poly J:C adjuvant.Immunizations occurred at 0 and 3 weeks, and sera from week 5 and week 7were tested for neutralization of RSV subtype A (RSV_A) and B (RSV_B).Mean values are indicated by horizontal red lines. Macaca mulattaanimals of Indian origin weighing 8.76-14.68 kg were intramuscularlyinjected with immunogens at week 0 and week 4. Blood was collected everyother week for up to 6 weeks. Four RSV-naïve rhesus macaques per groupwere immunized intramuscularly with 50 μg of the indicated RSV F proteinmixed with 500 μg of poly I:C adjuvant. Immunizations occurred at 0 and4 weeks, and sera from week 6 were tested for neutralization of RSVsubtype A (left) and B (right). Mean values are indicated by horizontalred lines. Taken together, these results show that the RSV_A F(+)FdTHSDSCav1 construct successfully generated a neutralizing response in miceand non-human primates.

Example 9 Structure-Based Design of a Fusion Glycoprotein Vaccine forRespiratory Syncytial Virus

Abstract. Respiratory syncytial virus (RSV) is the leading cause ofhospitalization for children under five years of age. To elicitprotective humoral responses against RSV, efforts were focused onantigenic site Ø, a metastable site specific to the prefusion state ofthe fusion (F) glycoprotein, as this site is the principal target ofhighly potent RSV-neutralizing antibodies elicited by natural infection.Structure-based design to engineer stabilized versions of F thatpreserved antigenic site Ø to extremes of pH and temperature was used.Six stabilized-F crystal structures provided atomic-level details forintroduced cysteine residues and filled hydrophobic cavities andrevealed subtly different “prefusion” F conformations. Immunization withsite Ø-stabilized variants of RSV F elicited—in both mice and non-humanprimates—RSV-specific neutralizing activity 3-15-fold higher than thoseelicited by RSV F in its postfusion state. Atomic-level design topresent a supersite of viral vulnerability can thus have atransformative effect on vaccine development.

Introduction. Respiratory syncytial virus (RSV) is estimated to beresponsible for 6.7% of deaths in children 1 mo-1 yr of age and causesexcess mortality in the elderly at levels comparable to that caused byinfection with influenza virus. Although RSV infection does not inducefully protective immunity, antibodies against the RSV fusion (F)glycoprotein can prevent severe disease in humans as demonstrated bypassive prophylaxis with the F-directed antibody, palivizumab(Synagis®).

The proven success of palivizumab has spurred vaccine efforts aimed ateliciting protective RSV F-directed antibodies. These efforts have beencomplicated by the structural diversity of RSV F, a type I fusionprotein that assumes at least two conformations: a metastable prefusionstate and a stable postfusion state. Both states share epitopes targetedby neutralizing antibodies, including that of palivizumab, andpostfusion RSV F is being developed as a vaccine candidate. As describedherein, the dominant target of RSV-neutralizing antibodies elicited bynatural infection was found to reside primarily on the prefusionconformation of RSV F, and antibodies such as AM22, and D25 (see, e.g.,U.S. Ser. No. 12/600,950, and U.S. Ser. No. 12/898,325)—substantiallymore potent than palivizumab—target antigenic site Ø, a metastable sitespecific to prefusion F, which is located at the membrane-distal apex ofthe prefusion RSV F trimer.

To enhance elicitation of these potent antibodies, engineered solublevariants of RSV F were designed to stably expose antigenic site Ø. Thesevariants were characterized both antigenically and crystallographically,and tested for immunogenicity in mice and non-human primates. Theresults provide insight into the interplay between design, antigenicity,structure, and immunogenicity and show how structure-based engineeringto preserve and to present an appropriate antigenic target can have atransformative effect on the elicitation of protective humoralresponses.

The structure-based vaccine strategy described herein included a fourstep strategy: (1) to identify a supersite of viral vulnerabilitytargeted by antibodies with potent neutralizing activity, (2) todetermine the structure of the supersite in complex with arepresentative antibody, (3) to engineer the stable presentation of thesupersite in the absence of recognizing antibody, and (4) to elicit hightiter protective responses through immunization with engineered antigensthat present the supersite (FIG. 26 ).

Engineering of RSV F Antigens

Because of its recognition by extraordinarily potent RSV-neutralizingantibodies, antigenic site Ø was chosen as the target supersite; itsstructure in complex with the D25 antibody is described herein (FIG.26B). To engineer variants of RSV F that stably presented site Ø, thestructure of RSV F bound by D25 was analyzed. Mechanistically, there area number of ways to stabilize a protein conformation. Mechanisms tostabilize site Ø without compromising its recognition were tested thesein combination with a T4-phage fibritin trimerization domain (“foldon”)(Efimov et al., J Mol Biol 242, 470 (1994); Boudko et al., Europeanjournal of biochemistry/FEBS 269, 833 (2002)) appended to the C-terminusof the RSV F ectodomain (McLellan et al., J. Virol. 85, 7788 (2011)).

Introducing cysteine pairs predicted to form a disulfide bond in thetarget conformation, but widely separated in alternative conformations,is one approach to stabilize a select structure. The β-carbons of serineresidues 155 and 290 are 4.4 Å apart in the D25-bound RSV F structure(see Example 1) and 124.2 Å apart in the postfusion structure (McLellanet al., J. Virol. 85, 7788 (2011; described above and see FIGS. 27 and32 ). A S155C-S290C double mutant, termed named “DS”, formed stable RSVF trimers, expressed at 1.4 mg/L, retained antigenic site Ø, and washomogeneous as judged by negative stain EM (described above; see alsoFIG. 31 , FIG. 33 ). Other cysteine modifications, such as those betweenregions of RSV F that are compatible with both the pre- and postfusionstates (e.g. S403C and T420C), did not stabilize antigenic site Ø (FIG.31 ). a number of potential inter-subunit double cysteine modificationswas also tested; none of the tested inter-subunit double cysteinesubstitutions, however, expressed more than 0.1 mg/L.

Cavity-filling hydrophobic substitutions provide another means tostabilize a select conformation. The D25-bound RSV F structure wasanalyzed for hydrophobic cavities unique to the D25-bound conformationof RSV F that abutted regions that differed in pre- and postfusion Fstates. A number of such cavities were identified in the membrane-distal“head” of the prefusion structure, close to the binding site of D25, andmodeled hydrophobic alterations to fill these cavities. S190F and V207Lalterations adopted prevalent side chain conformations with minimalclashes, while K87F, V90L, V220L and V296F alterations showed lesssteric compatibility. filling these cavities with pairs of changes wasassessed. A S190F-V207L pair, which was named “Cav1” (FIG. 27 ), formedstable RSV F trimers, expressed at 2.2 mg/L, and retained antigenic siteØ (FIG. 31 ). Meanwhile, K87F-V90L, S190F-V296F and V207L-V220L variantsshowed enhanced retention of D25 recognition, but less than 0.1 mg/lyields of RSV F trimer (FIG. 31 ).

Other cavities towards the center of prefusion RSV F were close to thefusion peptide, the trimer axis, and an acidic patch comprising residuesAsp486, Glu487, and Asp489. A number of cavity-filling alterations weremodeled including F137W, F140W, and F488W, and analyzed thesealterations in combination with D486H, E487Q, and D489H (FIG. 31 ). Ofthe six combinations tested, only two (F488W andD486H-E487Q-F488W-D489H) expressed levels of purified RSV F trimer atgreater than 0.1 mg/l and retained D25 recognition. TheD486H-E487Q-F488W-D489H variant, designated “TriC”, formed stable RSV Ftrimers, expressed at 0.8 mg/l, and retained antigenic site Ø (FIG. 31 ,FIG. 27 ).

The impact of destabilizing the postfusion conformation on thepreservation of antigenic site Ø was also tested. V178N, predicted tointroduce an N-linked glycan compatible with the prefusion but not thepostfusion conformation of F, did not appear to stabilize antigenic siteØ, nor did V185E or I506K, which would place a glutamic acid or a lysineinto the interior of the postfusion six-helix bundle (FIG. 31 ). Thesemutations likely result in some intermediate conformation of RSV F thatis “triggered”, but is unable to adopt the postfusion conformation. Inall, over 100 RSV F variants were constructed, expressed in a 96-welltransfection format (Pancera et al., PLoS ONE 8, e55701 (2013)), andtested by ELISA for binding to D25 and motavizumab. Fifteen constructswere compatible with D25 binding, six of which retained D25 recognitionfor at least 7 days at 4° C., and three of these could be purified tohomogeneous trimers that retained antigenic site Ø (FIG. 31 ). Overall,a strong correlation was observed between retention of D25 binding forat least 7 days at 4° C. in 96-well supernatants and yield of purifiedtrimers from large scale expression and purification (FIG. 34 ).

Combinatorial Optimization of Site Ø Stability

DS, Cav1, and TriC variants displayed a variety of physical andantigenic properties. The DS variant was the least stable to pH andtemperature extremes, but more permanently stabilized in the trimericstate, while constant interconversion from trimer to aggregate wasobserved for Cav1 and TriC. To assess whether a more optimal variant ofRSV F might be obtained by combining DS, Cav1, and TriC, allcombinations were made.

Combinations generally improved retention of D25 reactivity to physicalextremes. Thus, for example, all combinations showed improved stabilityto incubation at 50° C. or pH 10.0. However, the low tolerance tofreeze-thaw exhibited by TriC was also observed in both Cav1-TriC andDS-Cav1-TriC. Overall, the DS-Cav1 combination appeared optimal in termsof trimer yield and physical stability to extremes of temperature, pH,osmolality, and freeze-thaw (FIG. 31 , FIG. 35 ), and was homogeneous asjudged by negative stain EM (FIG. 33 ).

Crystallographic Analysis

To provide atomic-level feedback, crystal structures of siteØ-stabilized variants of RSV F were determined (FIG. 28 ). The DS, Cav1,DS-Cav1 and DS-Cav1-TriC variants all crystallized in similar 1.5 Mtartrate pH 9.5 conditions, and these cubic crystals diffracted X-raysto resolutions of 3.1 Å, 3.1 Å, 3.8 Å and 2.8 Å resolutions,respectively (FIG. 40 ). Molecular replacement solutions were obtainedby using the D25-bound RSV F structure as a search model, and theserevealed a single RSV F protomer in the asymmetric unit, with thetrimeric F axis aligned along the crystallographic threefold. Tetragonalcrystals of Cav1 and cubic crystals of DS-Cav1 were also obtained from1.7 M ammonium sulfate pH 5.5 conditions, and these diffracted toresolutions of 2.4 Å and 3.0 Å, respectively (FIG. 40 ). Molecularreplacement revealed the tetragonal lattice to have a full RSV F trimerin the asymmetric unit, and to be highly related to the tartrate cubiclattices. Overall these structures revealed the engineered RSV Fvariants to be substantially in the D25-bound conformation (Theengineered RSV F variants had C□-root mean square deviations from theD25-bound conformation between 0.68-1.5 Å and from the postfusionconformation of approximately 30 Å).

Although the structure of the DS variant (FIG. 28 , left most column)was stable as a soluble trimer, with the cysteine substituted residuesat 155 and 290 indeed forming a disulfide bond that largely preventedtriggering to the postfusion state, much of the membrane-distal portionof the RSV F trimer, including antigenic site Ø, was either disordered(residues 63-72 and 169-216) or in a different conformation. Thus, forexample, residues 160-168 in the DS structure extend the α2-helixinstead of forming a turn and initiating the α3-helix as in theD25-bound F structure (FIG. 28B, left most panel). One non-limitingexplanation for the differences between DS structure and the D25-boundRSV F structure is that the crystallized DS is in a conformation thatdoes not bind D25. Overall the DS variant retained many of the featuresof the prefusion state of RSV F, including the fusion peptide in theinterior of the trimeric cavity.

In comparison to DS, the Cav1 structure (FIG. 28 , 2^(nd) and 3^(rd)columns) was more ordered in the membrane-distal apex, with theα3-helix, β3/β4 hairpin, and the α4-helix clearly defined. Residues137-202, which contain the S190F substitution, had a Cα-rmsd of 0.6 Åwhen compared to the D25-bound F structure. The higher degree ofstructural order was likely due to the S190F mutation that filled acavity observed in the D25-bound F structure, and increased van derWaal's contacts with residues Ile57, Lys176, Val192, Glu256, Ser259 andLeu260. The other cavity-filling mutation in Cav1, V207L, was shifted by5.5 Å compared to the D25-bound F structure, with the C-terminal portionof the α4-helix kinking near Pro205 and adopting distinct conformationsin the two crystallization conditions (FIG. 28B, 2^(nd) and 3^(rd)panels from left).

A striking feature of the Cav1 structure in the tetragonal crystallattice is the C-terminus of F₂, which is disordered in the D25-bound Fstructure, but in Cav1, tunnels into the trimeric cavity alongside thefusion peptide. Interestingly, the C-terminus ends with Ala107, and notArg109, as expected after cleavage of the furin site(Arg106-Ala107-Arg108-Arg109). In the Cav1 structure, the positivecharge of Arg106 is offset by an ordered sulfate ion (FIG. 28C).Biologically, the interior position of the F₂ C-terminus may play a rolein triggering of the prefusion F conformation.

Comparison of the DS-Cav1 structures from the two tetragonal crystalforms (FIG. 28 , 2^(nd) and 3^(rd) columns from right) to those of Cav1revealed only minor differences (Cα rmsd of 0.86 Å for residues betweenCav1 and DS-Cav1 grown in ammonium sulfate conditions; Cα rmsd of 0.47 Åfor 447 residues in the cubic lattice). The largest differences occurredat the RSV F apex, including antigenic site Ø and specifically atresidues 64-73 and 203-216. Notably, the atomic mobility (B-factor) washighest in this apex region for all of the site Ø-stabilized variants,perhaps indicative of intrinsic site Ø flexibility. Interestingly,however, site Ø has low atomic mobility when bound by D25, revealing theability of D25 to stabilize both overall and local RSV F conformations.

The structure of the DS-Cav1-TriC triple combination (FIG. 28 , farright column) was also highly similar to other Cav1-containing RSV Fvariant structures. One difference in the electron density, however,corresponded to an expanse of weak density at the membrane-proximalregion, which corresponded to the dimensions of the T4-fibritintrimerization domain (Stetefeld et al., Structure 11, 339 (2003)), whichis not visible in other crystallized RSV F structures which containedthis domain, including the D25-bound structure. Small structuraldifferences in packing likely allow for the partial ordering of thisdomain (and may also account for its increased diffraction limit of theDS-Cav1-TriC crystals relative to the other cubic variants), rather thandifferences in the interaction between the DS-Cav1-TriC stabilized RSV Fand this trimerization domain.

In terms of the TriC alterations of residues 486-489, the critical F488Wsubstitution packed directly against the F488W substitutions ofneighboring protomers of the RSV F trimer. The indole side chain ofTrp488 pointed towards the trimer apex and also formed ring-stackinginteractions with the side chain of 140Phe of the fusion peptide (FIG.28C, far right panel). This fusion peptide interaction, which is notobserved in any of the Phe488-containing structures, likely inhibits theextraction of the fusion peptide from the prefusion trimer cavity,providing a structural rationale for the ability of the F488W alterationto stabilize the prefusion state of RSV F (FIG. 31 ).

Immunogenicity of Antigenic Site Ø-Stabilized RSV F

To assess the effect of site Ø-stabilization on the elicitation ofRSV-protective humoral responses, CB6 mice were immunized with variousforms of RSV F, injecting each mouse with 10 μg RSV F combined with 50μg poly I:C adjuvant at weeks 0 and 3, and measured the ability of week5 sera to prevent RSV infection of HEp-2 cells. DS, Cav1, and TriC eachelicited high titers of neutralizing activity (geometric mean 50%effective concentrations (EC₅₀s) of 1826-2422). This level was ˜3-foldhigher than elicited by postfusion F (504 EC₅₀), and ˜20-fold higherthan the protective threshold. By comparison, DS-Cav1 elicitedneutralizing activity of 3937 EC₅₀, roughly 7-fold higher thanpostfusion F and 40-fold higher than the protective threshold (FIG.29A). (When palivizumab (Synagis®) is dosed at a concentration of 15mg/kg, serum levels at trough are ˜40 μg/ml, which provides protectionin infants from severe disease. In the neutralization assay, 40 μg/ml ofpalivizumab in serum yields an EC50 of 100. This titer is alsoassociated with complete protection from lower respiratory tractinfection in mice and cotton rats challenged with RSV.)

To quantify the elicitation of antibodies between different sites onprefusion RSV F, antigenic site Ø-occluded forms of RSV F were utilized.CB6 mice immunized with 20 μg RSV F bound by antigenic site Ø-directedantibodies (comprising ˜10 μg of RSV F and ˜10 μg of the antigen-bindingfragment of antibody) developed week 5 geometric mean neutralizingtiters of 911 and 1274 EC₅₀ for AM22 and D25 complexes, respectively,roughly double that of postfusion at 10 μg/ml and comparable to thoseelicited by postfusion at 20 μg/ml (FIG. 29A). These findings suggestthat the very high titers elicited by immunization with RSV F variantsstabilized in the prefusion state—especially DS-Cav1—were due toantibodies targeting antigenic site 0.

To examine the generality of site Ø elicitation, rhesus macaques wereimmunized with DS-Cav1, DS and postfusion forms of RSV F, injecting eachmacaque with 50 μg RSV F mixed with 500 μg poly I:C adjuvant at weeks 0and 4 and measuring the ability of week 6 sera to inhibit RSV infection.Formulated proteins retained expected antigenic profiles as measured byD25 binding (FIG. 38 ). DS and DS-Cav1 elicited geometric mean titers of1222 and 2578 EC₅₀, respectively, roughly 5- and 10-fold higher thanpostfusion F (287 EC₅₀) (FIG. 29B), thereby demonstrating a conservationof the relative immunogenicity for the different forms of RSV Fimmunogen between mice and primates, and the ability of DS-Cav1 togenerate high RSV-protective titers in a primate immune system.

Optimization of RSV F Protective Responses

The matrix of information (FIG. 26C) generated by the interplay betweendesign, physical and antigenic properties, atomic-level structure, andimmunogenicity provides a basis for further optimization (Nabel, Science326, 53 (2009)). For example, to obtain insight into the relationshipbetween various antigenic and physical properties of engineered RSV Fsand the elicitation of RSV-protective responses, one can correlateproperties (FIG. 31 ) with immunogenicity (FIG. 29 ). Such correlationsindicate that increasing site Ø stability to physical extremes (but nottrimer yield nor D25 affinity) should increase protective titerselicited upon immunization (FIG. 30A), thereby providing design insightinto further optimization. Similarly, correlations between variousconformational states or regions of RSV F (FIG. 28 ) and immunogenicity(FIG. 29 ) provide design insight into the conformation of RSV F thatprovides the most protective responses. In this case, the resultsindicate that enhancing structural mimicry of antigenic site Ø in itsD25-bound conformation should lead to improved protective titers (FIG.30B).

In addition to providing direction for improvement, the matrix ofinformation can also provide an estimate for the degree that suchimprovement can occur. That is, once a correlation has been establishedsay between physical stability or structural mimicry and protectiveresponses, one can maximize physical stability (e.g. to 100% retentionof D25 binding) or structural mimicry (e.g. to exact mimicry of theD25-bound conformation) to gain an idea of the maximal improvement ofthe elicited protective response relative to that particular parameter.These results (FIG. 30A,B) suggest that additional structural mimicrywould likely not have much effect on immunogenicity, but additionalphysical stabilization of antigenic site Ø might substantially improvethe antigenic quality of the protective titers. Independent parameterssuch as adjuvant, multimerization, or immunization regimes are likely toallow improvement of the elicited response, and such parameters can beindependently analyzed and optimized (Flexibility of an antigenic sitemay increase its immunogenicity by allow the site to conform to a widerdiversity of antibodies. We note in this context that theatomic-mobility factors of antigenic site Ø were among the highest inthe RSV F ectodomain).

Experimentally mixing parameters can also provide insight. For example,to determine the focus of RSV F-elicited sera, immunogenicity can beinterrogated antigenically (FIG. 30C). To measure the antigenicity ofsera elicited by different forms of RSV F, the different forms of RSV Fwere coupled to an Octet biosensor tip, and measured the reactivity ofelicited sera as well as “preabsorbed” sera, to which different forms ofRSV Fs had been added (FIG. 30C). With DS-Cav1 on the sensor, biosensorresponses to postfusion F-, DS-, and DS-Cav1-immunized macaques showedincreasing responses (FIG. 30C, left panel); with postfusion F on thesensor, biosensor responses to the same sera showed decreasing responses(FIG. 30C, right panel); and with sera that had been preabsorbed withpostfusion F and with DS-Cav1 on the sensor, responses from postfusionF-, DS- and DS-Cav1-immunized macaques trending with elicited titers ofprotection (FIG. 30C left panel). Overall, elicited EC₅₀ titers did nottrend with antigenic responses measured against either prefusion orpostfusion forms of RSV F, but did correlate with the level ofprefusion-specific responses, either measured as a difference or as aratio (p=0.005) between prefusion and postfusion RSV F-directedresponses (FIG. 30D) (For the “prefusion” form of RSV F, the DS-Cav1stabilized variant of RSV F was used). These results suggest that thequality of the immune response is substantially better for RSV Fimmunogens in the prefusion versus the postfusion conformation, afinding that may relate to the superior neutralization potency observedfor prefusion-specific antibodies that target antigenic site Ø (itshould be possible to deconvolute the elicited response, by usingstructurally defined probes, as shown with D25 and motavizumab-bond RSVF in FIG. 39 ).

Without being bound by theory, antigenic sites that contain multipleepitopes targeted by antibodies that derive from multiple germline genesmay be ideal vaccine targets since these “supersites” have a highprobability of eliciting multiple lineages of neutralizing antibodies.Antigenic site Ø on RSV F is an example of an antigenic supersite thatis also a site of viral vulnerability. Many of the lessons learned fromthe efforts with RSV described herein, such as the importance ofexamining the natural human immune response and of selecting theappropriate target site, are likely to be generally applicable. Overall,by focusing structure-based design on supersites of vulnerability,structural vaccinology may be on the brink of achieving aparadigm-altering shift in the development of vaccines against viralpathogens.

Materials and Methods

Viruses and cells. Viral stocks were prepared and maintained aspreviously described (Graham et al., J. Med. Virol. 26, 153 (1988)).RSV-expressing Green Fluorescent Protein (GFP) RSV-GFP was constructedand provided as previously reported (Hallak et al., Virology 271, 264(2000)). The titer of the RSV-GFP stocks used for flow cytometry-basedneutralization and fusion assays was 2.5×10⁷ pfu/ml. The titer of theRSV A2 stock used for attachment assay was 1.02×10⁸ pfu/ml. HEp-2 cellswere maintained in Eagle's minimal essential medium containing 10% fetalbovine serum (10% EMEM) and were supplemented with glutamine, penicillinand streptomycin.

Expression and purification of antibodies and Fab fragments. Antibodieswere expressed by transient co-transfection of heavy and light chainplasmids into HEK293F cells in suspension at 37° C. for 4-5 days (seeabove, and also McLellan et al., Nat Struct Mol Biol 17, 248 (2010);McLellan et al., J Virol 84, 12236 (2010)). The cell supernatants werepassed over Protein A agarose, and bound antibodies were washed with PBSand eluted with IgG elution buffer into 1/10th volume of 1 M Tris-HCl pH8.0. Fabs were created by digesting the IgG with Lys-C or HRV3C protease(McLellan et al., Nature 480, 336 (2011)), and the Fab and Fc mixtureswas passed back over Protein A agarose to remove Fc fragments. The Fabsthat flowed through the column was further purified by size exclusionchromatography.

Screening of prefusion-stabilized RSV F constructs. Prefusion RSV Fvariants were derived from the RSV F (+) Fd construct (see Example 1),which consists of RSV F residues 1-513 with a C-terminal T4 fibritintrimerization motif (McLellan et al., Nature 480, 336 (2011)), thrombinsite, 6× His-tag, and StreptagII. A 96-well microplate-formattedtransient gene expression approach was used to achieve high-throughputexpression of various RSV F proteins as described previously (Pancera etal., PLoS ONE 8, e55701 (2013)). Briefly, 24 hours prior to transfectionHEK 293T cells were seeded in each well of a 96-well microplate at adensity of 2.5×10⁵ cells/ml in expression medium (high glucose DMEMsupplemented with 10% ultra-low IgG fetal bovine serum and1×-non-essential amino acids), and incubated at 37° C., 5% CO₂ for 20 h.Plasmid DNA and TrueFect-Max (United BioSystems, MD) were mixed andadded to the growing cells, and the 96-well plate was incubated at 37°C., 5% CO₂. One day post transfection, enriched medium (high glucoseDMEM plus 25% ultra-low IgG fetal bovine serum, 2× non-essential aminoacids, 1× glutamine) was added to each well, and returned to incubatorfor continuous culture. On day five post transfection, the expressed RSVF protein in the supernatant was harvested and tested by ELISA forbinding to D25 and motavizumab antibodies using Ni²⁺-NTA microplates.After incubating the harvested supernatants at 4° C. for one week, theELISAs were repeated.

Large-scale expression and purification of RSV F constructs. Solublepostfusion RSV F was expressed and purified as described previously(McLellan, J Virol 85, 7788 (2011)). Prefusion variants were expressedby transient transfection in Expi293F cells using TrueFect-Max (UnitedBioSystems, MD). The culture supernatants were harvested 5 days posttransfection and centrifuged at 10,000 g to remove cell debris. Theculture supernatants were sterile filtered prior to buffer exchange andconcentrated using tangential flow filtration (van Reis, J Membrane Sci159, 133 (1999)). RSV F glycoproteins were purified by immobilizednickel- and streptactin-affinity chromatography, and relevant fractionscontaining the RSV F variants were pooled, concentrated and subjected tosize-exclusion chromatography (see Example 1). Affinity tags wereremoved by digestion with thrombin followed by size exclusionchromatography. Glycoproteins used in the non-human primateimmunizations were tested for endotoxins using the limulus amebocytelysate assay and if necessary, proteins were passed over an EndoTrap Red(BioVendor) column to remove endotoxins prior to immunizations.Endotoxin level was <5 EU/kg body weight/hr, as measured by the EndpointChromogenic Limulus Amebocyte Lysate (LAL) test kit (Lonza, Basel,Switzerland).

Stabilized RSV F antigenic characterization. A fortéBio Octet Red384instrument was used to measure binding kinetics of RSV F to antibodiesthat target antigenic site Ø (D25, AM22), site I (131-2a), site II(pavlizumab, motavizumab) and site IV (101F). All assays were performedwith agitation set to 1,000 rpm in phosphate-buffered saline (PBS)supplemented with 1% bovine serum albumin (BSA) in order to minimizenonspecific interactions. The final volume for all solutions was 100μl/well. Assays were performed at 30° C. in solid black 96-well plates(Geiger Bio-One). StreμMAB-Immo (35 μg/ml) in PBS buffer was used toload anti-mouse Fc probes for 300 s, which were then used to capturerelevant RSV F variant proteins that contained a C-terminal Strep-tag.Typical capture levels for each loading step were between 0.7 and 1 nm,and variability within a row of eight tips did not exceed 0.1 nm foreach of these steps. Biosensor tips were then equilibrated for 300 s inPBS+1% BSA prior to measuring association with antigen binding fragments(Fabs) in solution (0.002 μM to 1 μM) for 300 s; Fabs were then allowedto dissociate for 400 s-1200 s depending on the observed dissociationrate. Dissociation wells were used only once to prevent contamination.Parallel correction to subtract systematic baseline drift was carriedout by subtracting the measurements recorded for a loaded sensorincubated in PBS+1% BSA. To remove nonspecific binding responses, aHIV-1 gp120 molecule with a C-terminal Strep-tag was loaded onto theanti-mouse Fc probes and incubated with RSV Fabs, and the nonspecificresponses were subtracted from RSV F variant response data. Dataanalysis and curve fitting were carried out using Octet software,version 7.0. Experimental data were fitted with the binding equationsdescribing a 1:1 interaction. Global analyses of the complete data setsassuming reversible binding (full dissociation) were carried out usingnonlinear least-squares fitting allowing a single set of bindingparameters to be obtained simultaneously for all concentrations used ineach experiment.

Physical stability of RSV F variants. To assess the physical stabilityof designed RSV F proteins under various stress conditions, the proteinswere treated with a variety of pharmaceutically relevant stresses suchas extreme pH, high temperature, low and high osmolality as well asrepeated freeze/thaw cycles. The physical stability of treated RSV Fproteins was evaluated by their degree of preservation of antigenic siteØ after treatment, a critical parameter assessed by binding of the siteØ-specific antibody D25.

In the pH treatment, RSV F protein was diluted to an initialconcentration of 50 μg/ml, adjusted to pH 3.5 and pH 10 with appropriatebuffers and incubated at room temperature for 60 minutes beforeneutralized back to pH7.5 and adjusted to 40 μg/ml. In the temperaturetreatment, RSV protein at 40 μg/ml was incubated at 50° C., 70° C. and90° C. for 60 minutes in PCR cyclers with heated lids to preventevaporation. In the osmolality treatment, 100 μl of RSV F proteinsolutions (40 μg/ml) originally containing 350 mM NaCl were eitherdiluted with 2.5 mM Tris buffer (pH 7.5) to an osmolality of 10 mM NaClor adjusted with 4.5 M MgCl2 to a final concentration of 3.0 M. Theprotein solutions were incubated for 60 minutes at room temperature andthen brought back to 350 mM NaCl by adding 5M NaCl or dilution with 2.5mM Tris buffer, respectively, before concentration down to 100 μl. Thefreeze/thaw treatment was carried out 10 times by repeated liquidnitrogen freezing and thawing at 37° C. Binding of antibody D25 to thetreated RSV F proteins were measured with an Octet instrument withprotocols described above. The degrees of physical stability were shownas the ratio of steady state D25-binding level before and after stresstreatment.

Crystallization and X-ray data collection of prefusion-stabilized RSV Fproteins. Crystals of RSV F DS, Cav1, DSCav1, and DSCav1TriC were grownby the vapor diffusion method in hanging drops at 20° C. by mixing 1 μlof RSV F with 1 μl of reservoir solution (1.4 M K/Na tartrate, 0.1M CHESpH 9.5, 0.2 M LiSO₄). Crystals were directly frozen in liquid nitrogen.Crystals of RSV F Cav1 and DSCav1 were also grown by the vapor diffusionmethod in hanging drops at 20° C. by mixing 1 μl of RSV F with 0.5 μl ofreservoir solution (1.7 M ammonium sulfate, 0.1 M citrate pH 5.5).Crystals were transferred to a solution of 3.2 M ammonium sulfate, 0.1 Mcitrate pH 5.5, and flash frozen in liquid nitrogen. All X-raydiffraction data were collected at a wavelength of 1.00 Å at the SER-CATbeamline ID-22.

Structure determination, refinement and analysis of prefusion-stabilizedRSV F.

X-ray diffraction data were integrated and scaled with the HKL2000 suite(Otwinowski and Minor, in Methods Enzymol. (Academic Press, 1997), vol.276, pp. 307-326)), and molecular replacement solutions were obtained byPHASER (McCoy et al., Phaser crystallographic software. J. Appl.Crystallogr. 40, 658 (2007)) using the D25-bound RSV F structure (PDBID: 4JHW, (see example 1)) as a search model. Manual model building wascarried out using COOT (Emsley et al., Acta Crystallogr D BiolCrystallogr 66, 486 (2010)), and refinement was performed in PHENIX(Adams et al., Acta Crystallogr D Biol Crystallogr 66, 213 (2010)).Final data collection and refinement statistics are presented in FIG. 40. Superimpositions of RSV F structures were performed using residues225-455 which showed high levels of structural similarity. Antigenicsite Ø rmsd calculations were based on residues 61-71 and 194-219 whichwere within 10 Å of the D25 antibody in the RSV F-D25 complex structure.

Negative staining electron microscopy analysis. Samples were adsorbed tofreshly glow-discharged carbon-film grids, rinsed twice with buffer, andstained with freshly made 0.75% uranyl formate. Images were recorded onan FEI T20 microscope with a 2k×2k Eagle CCD camera at a pixel size of1.5 Å. Image analysis and 2D averaging was performed with Bsoft(Heymann, J. Struct. Biol. 157, 3 (2007)) and EMAN (Ludtke et al., J.Struct. Biol. 128, 82 (1999)).

NHP immunizations. All animal experiments were reviewed and approved bythe Animal Care and Use Committee of the Vaccine Research Center, NIAID,NIH, and all animals were housed and cared for in accordance with local,state, federal, and institute policies in an American Association forAccreditation of Laboratory Animal Care (AAALAC)-accredited facility atthe NIH. Macaca mulatta animals of Indian origin weighing 8.76-14.68 kgwere intramuscularly injected with immunogens at week 0 and week 4.Blood was collected every other week for up to 6 weeks.

RSV neutralization assays. Sera were distributed as four-fold dilutionsfrom 1:10 to 1:40960, mixed with an equal volume of recombinantmKate-RSV expressing prototypic F genes from strain A2 and the Katushkafluorescent protein, and incubated at 37° C. for one hour. Next, 50 μlof each serum dilution/virus mixture was added to HEp-2 cells that hadbeen seeded at a density of 1.5×10⁴ in 30 μl MEM (minimal essentialmedium) in each well of 384-well black optical bottom plates, andincubated for 20-22 hours before spectrophotometric analysis at Ex 588nm and Em 635 nm (SpectraMax Paradigm, Molecular Devices, Sunnyvale, CA94089). The IC₅₀ for each sample was calculated by curve fitting andnon-linear regression using GraphPad Prism (GraphPad Software Inc., SanDiego CA). P values were determined by Student's T-test.

Sera antigenicity analysis. A fortéBio Octet Red384 instrument was usedto measure sera reactivity to RSV F variant proteins with agitation,temperature, 96-well plates, buffer and volumes identical to those usedfor kinetic measurements. RSV F DSCav1 and postfusion F were immobilizedto amine coupling probes via probe activation in a EDC/NHS activationmixture for 300 s in 10 mM acetate pH 5. The probe reactivity wasquenched using 10 mM ethanolamine pH 8.5. Typical capture levels werebetween 0.7 and 1 nm, and variability within a row of eight tips did notexceed 0.1 nm for each of these steps. Biosensor tips were thenequilibrated for 300 s in PBS+1% BSA buffer prior to bindingmeasurements. Sera were diluted to a 1/50 and 1/100 dilution in PBS+1%BSA and binding was assessed for 300s. Sera depletion was carried out byusing 1 μg of DSCav1 or postfusion F proteins per 1 μl of animal sera.Parallel correction to subtract non-specific sera binding was carriedout by subtracting binding levels of an unloaded probe incubated withthe sera. Site-specific antigenicity was assessed by incubating the RSVF variant-loaded probes with 1 or 2 μM D25 Fab for site Ø assessment andmotavizumab Fab for site II assessment or both antibodies to assess theremaining non-site Ø/II reactivity.

Example 10 Single Chain RSV F Proteins Stabilized in a PrefusionConformation

This example illustrates additional recombinant RSV F proteins that lackthe native furin cleavage sites, such that the F protein protomer isformed as a single polypeptide chain, instead of a F₂/F₁ heterodimer.Schematic diagrams illustrating design of the additionalprefusion-stabilized single-chain RSV F proteins are provided in FIGS.43 and 44 .

FIGS. 43-45 illustrate the design of a series of single chainconstructs, including single-chain RSV F construct no. 9 (scF no. 9;BZGJ9 DSCav1; SEQ ID NO: 669). Variables for the single chain constructsinclude the linker size, the F1 and F2 end points and the mechanism usedto induce trimerization of the single chain construct. Additionally,several strategies can be employed to stabilize the single chainconstructs in a prefusion conformation, including use of the strategiesdescribed herein. The indicated single chain constructs were expressedin cells and characterized by size exclusion chromatography (FIG. 46 )and binding to RSV F specific antibodies (FIG. 47 ).

To further characterize the RSV F construct no. 9 (scF no. 9; BZGJ9DSCav1; SEQ ID NO: 669), the three dimensional structure of this proteinwas solved by X-ray crystallography (see FIGS. 48-51 ). Cubic crystalswere grown using the vapor diffusion method in a reservoir solution of1.19 M Li₂SO₄, 3.33% PEG 400, 0.12 M MgSO₄, 0.1 M NaOAc pH 5.5. Crystalsgrew to ˜120 μm before they were flash-frozen in a reservoir solutioncontaining 2 M lithium sulfate. The diffraction data was collected to aresolution of 3.2 Å with an intensity over error of 2.84. The crystalstructure illustrated the location of the GS linker in construct No. 9(FIGS. 49 and 50 ), was used to predict the location of other linkersizes (FIG. 51 ), and as the basis of the design of additional singlechain constructs BZGJ9-1 through 9-10 (see FIG. 55 ). Single-chainconstruct codon-optimized genes with a C-terminal T4 fibritintrimerization motif, thrombin site, 6× His-tag, and StreptagII wassynthesized and subcloned into a mammalian expression vector derivedfrom pLEXm. Plasmids expressing RSV F(+) Fd, were transfected intoHEK293 GnTI−/− Cells in suspension. After 4-5 days, the cell supernatantwas harvested, centrifuged, filtered and concentrated. The protein wasinitially purified via Ni2+-NTA resin (Qiagen, Valencia, CA) using anelution buffer consisting of 20 mM Tris-HCl pH 7.5, 200 mM NaCl, and 250mM imidazole pH 8.0. The complex was then concentrated and furtherpurified over StrepTactin resin as per the manufacturer's instructions(Novagen, Darmstadt, Germany). After an overnight incubation withthrombin protease (Novagen) to remove the His and Strep tags, an excessof D25 Fab was added to the complex, which was then purified on aSuperdex-200 gel filtration column (GE Healthcare) with a running bufferof 2 mM Tris-HCl pH 7.5, 350 mM NaCl, and 0.02% NaN3 or phosphatebuffered saline (PBS) pH7.4. Single-chain-Ferritin single gene productswere expressed and purified in a similar manner.

Several single chain constructs were selected for immunogenicity testingin animal models (FIG. 53 ). BZGJ9 DS-Cav1, BZGJ9, BZGJ11 DS-Cav1(monomer), BZGJ10 (monomer and trimer fractions), BZGJ8 (monomer), BZGJ4DS-Cav1 and BZGJ11 DS-Cav1-Lumazine synthase (60mer oligomer) were alltested for immunogenicity in groups of 10 CB6F1/J mice by injecting 10ug of protein in the presence of 50 ug Poly I:C at week 0 and week 3.Sera from week 5 was tested for immunogenicity. Control groups of RSV Fsubtype A DS-Cav1 and Postfusion protein were also tested and immunizedin a similar manner.

To assess neutralization against RSV subtype A and Subtype B, sera fromimmunized animals were distributed as four-fold dilutions from 1:10 to1:40960, mixed with an equal volume of recombinant mKate-RSV expressingprototypic F genes from subtype A (strain A2) or subtype B (strain18537) and the Katushka fluorescent protein, and incubated at 37° C. for1 h. Next, 50 μl of each serum dilution/virus mixture was added to HEp-2cells that had been seeded at a density of 1.5×10⁴ in 30 μl MEM (minimalessential medium) in each well of 384-well black optical bottom plates,and incubated for 20-22 h before spectrophotometric analysis at 588 nmexcitation and 635 nm emission (SpectraMax Paradigm, Molecular Devices,CA). The IC50 for each sample was calculated by curve fitting andnon-linear regression using GraphPad Prism (GraphPad Software Inc., CA).P-values were determined by Student's t-test.

The neutralization results show that all tested single chain constructsare immunogenic.

The single chain constructs were linked to ferritin to produce ferritinnanoparticles including the scF antigens (FIG. 56 ). Briefly, theC-terminus of the F1 polypeptide included in the scF protein was linkedto ferritin, and the recombinant protein was expressed in cells toproduce scF-ferritin nanoparticles. One example is the“BZGJ9-DS-Cav1-LongLink-Ferritin” protein (SEQ ID NO: 1429), whichincludes a recombinant RSV F single chain protein including a GS linkerbetween RSV F positions 105 and 145 and a ferritin subunit linked toposition 513 of the RSV F protein by a heterologous peptide linkergenerated by linking the C-terminus of the F1 polypeptide in scF no. 9to a ferritin subunit. The scF-ferritin nanoparticles were expressed,purified, and characterized for temperature, pH, and osmolaritystability (FIG. 57 ). Additionally, the ferritin nanoparticles wereadministered to animals to demonstrate that they are immunogenic (FIG.58 ). The three constructs tested were RSV F DSCav1 (SEQ ID NO: 371),BZGJ9-DS-Cav1-LongLink-Ferritin (SEQ ID NO: 1429), and scF no. 9 (alsotermed BZGJ9 DS-Cav1, SEQ ID NO: 669). These are the sameimmunogenicity/neutralization as described above.

Several single chains sequences are provided in the SEQ ID NOs listed inTable 19, as well as an indication of design approach.

TABLE 19 Exemplary Single Chain RSV F proteins Back- SEQ ID Name Conceptground Mutations NO Non-cleavable Foldon BZGJ9-1 SC BZGJ9-DS-Cav1G linker between 698 w/IL residue 105 to 145 BZGJ9-2 SC BZGJ9-DS-Cav1GG linker between 699 w/IL residue 105 to 145 BZGJ9-3 SC BZGJ9-DS-Cav1GQG linker between 700 w/IL residue 105 to 145 BZGJ9-4 SC BZGJ9-DS-Cav1GGSG (Seq_1443) 701 w/IL linker between residue 105 to 145 BZGJ9-5SC BZGJ9-DS-Cav1 GGSG (Seq_1443) 702 w/IL linker betweenresidue 105 to 145 BZGJ9-6 SC BZGJ9-DS-Cav1 GGSG (Seq_1443) 703 W/ILlinker between residue 105 to 145 BZGJ9-7 SC BZGJ9-DS-Cav1GGSGGS (Seq_1444) 704 w/IL linker between residue 105 to 145 BZGJ9-8SC BZGJ9-DS-Cav1 GGSGGSG (Seq_1445) 705 w/IL linker betweenresidue 105 to 145 BZGJ9-9 SC BZGJ9-DS-Cav1 Fusion of residue 103 706w/IL to 145 BZGJ9-10 SC BZGJ9-DS-Cav1 GS linker between 707 w/ILresidue 103 to 145 Cleavable Foldon SCRSVF9aCCextxFd Inter-DS BZGJ9a xFd512CChnvnagkstt (Res. 708 (SeqID 512-523 of SEQ ID NO: 669 w/o 844)DSCav1 mut.) SCRSVF9aC485C494xFd Inter-DS BZGJ9a xFd 485C, 494C 709SCRSVF9aC519C520extx Inter-DS BZGJ9a xFd 512LLhnvnaCCstt (Res. 710 Fd475-486 of SEQ ID NO: 71-) SCRSVF9aC99C362xFd Inter-DS BZGJ9a xFd99C, 362C 711 SCRSVF9aC99C361xFd Inter-DS BZGJ9a xFd 99C, 361C 712SCRSVF9aC153C461xFd Inter-DS BZGJ9a xFd 153C, 461C 713SCRSVF9aC102C359xFd Inter-DS BZGJ9a xFd 102C, 359C 714 SCRSV F 9axFd xFdBZGJ9a xFd 512LLSAI 715 SCRSV F 9aextxFd xFd BZGJ9a xFd512LLhnvnagkstt (Res. 716 475-486 of SEQ ID NO: 716)Ferritin Particles-No Foldon OpFer1 ES of RSV F BZGJ9a Fer S190V 717OpFer2 ES of RSV F BZGJ9a Fer K226L 718 OpFer3 ES of RSV F BZGJ9a FerT58I, A298M 719 OpFer4 ES of RSV F BZGJ9a Fer S190V, K226L 720 OpFer5ES of RSV F BZGJ9a Fer S190V, T58I, A298M 721 OpFer6 ES of RSV F BZGJ9aFer K226L, T58I, A298M 722 OpFer7 ES of RSV F BZGJ9a FerT58I, A298M, S190V, 723 K226L OpFer8 ES of RSV F BZGJ9a Fer Cav1 724OpFer9 ES of RSV F BZGJ9a Fer NoMutationsSC9a 725 OpFer10 ES of RSV FBZGJ9a Fer S190V with optimized 726 coil coil-8aa linker OpFer11ES of RSV F BZGJ9a Fer S190V With CC and 727 optimized coiled coil-8 aa linker OpFer12 ES of RSV F BZGJ9a Fer S190V 728FIRKSDELLSAIGGYIPSAPS GSG-Fer (Res. 495-518 of SEQ ID NO: 728 OpFer13ES of RSV F BZGJ9a Fer S190V SC-Foldon-8aa- 729 Fer OpFer14 ES of RSV FBZGJ9a Fer S190V optimized 730 leader Non-cleavable Foldon OpFd1ES of RSV F BZGJ9a Fd S190V 731 OpFd2 ES of RSV F BZGJ9a Fd K226L 732OpFd3 ES of RSV F BZGJ9a Fd T58I, A298M 733 OpFd4 ES of RSV F BZGJ9a FdS190V, K226L 734 OpFd5 ES of RSV F BZGJ9a Fd S190V, T58I, A298M 735OpFd6 ES of RSV F BZGJ9a Fd K226L, T58I, A298M 736 OpFd7 ES of RSV FBZGJ9a Fd T58I, A298M, S190V, 737 K226L OpFd8 ES of RSV F BZGJ9a FdS190F, V207L 738 OpFd9 ES of RSV F BZGJ9a Fd NoMutationsSC9a 739 OpFd10ES of RSV F BZGJ9a Fd S190V with optimized 740 coil coil OpFd11ES of RSV F BZGJ9a Fd S190V With CC and 741 optimized coiled coil OpFd14ES of RSV F BZGJ9a Fd S190V optimized 742 leader OpFd14 ES of RSV FBZGJ9a Fd S190V optimized 743 leader Cleavable FoldonSCRSVF9a 74C218C xFd Inter-DS BZGJ9a xFd 74C, 218C 744 SCRSVF9a 146C460CInter-DS BZGJ9a xFd 146C, 460C 745 xFd SCRSVF9a 149C458C Inter-DS BZGJ9axFd 149C, 458C 746 xFd SCRSVF9a 374C454C Inter-DS BZGJ9a xFd 374C, 454C747 xFd SCRSVF 74C218C xFd Inter-DS SEQ_669 xFd 74C, 218C 748 (BZGJ9DSCav1) SCRSVF 146C460C xFd Inter-DS BZGJ9 xFd 146C, 460C 749 DSCav1SCRSVF 149C458C xFd Inter-DS BZGJ9 xFd 149C, 458C 750 DSCav1SCRSVF 374C454C xFd Inter-DS BZGJ9 xFd 374C, 454C 751 DSCav1SCRSVF9 C485C494xFd Inter-DS BZGJ9 xFd 485C, 494C 752 DSCav1 SCRSVF9Inter-DS BZGJ9 xFd 519C, 520C 753 C519C520extxFd DSCav1SCRSVF9 C99C362xFd Inter-DS BZGJ9 xFd 99C, 362C 754 DSCav1SCRSVF9 C99C361xFd Inter-DS BZGJ9 xFd 99C, 361C 755 DSCav1SCRSVF9 C153C461xFd Inter-DS BZGJ9 xFd 153C, 461C 756 DSCav1SCRSVF9 C102C359xFd Inter-DS BZGJ9 xFd 102C, 359C 757 DSCav1Non-Cleavable Foldon BZGJ9pi I217W Inter-DS BZGJ9 Fd I217W 758 DSCav1BZGJ9pi I221W Inter-DS BZGJ9 Fd I221W 759 DSCav1 BZGJ9pi D486F Inter-DSBZGJ9 Fd H486F 760 DSCav1 BZGJ9pi T400F Inter-DS BZGJ9 Fd T400F 761DSCav1 BZGJ9pi V278F Inter-DS BZGJ9 Fd V278F 762 DSCav1BZGJ9pi Q224D, L78K Inter-DS BZGJ9 Fd Q224D, L78K 763 DSCav1BZGJ9pi I217W, I221W Inter-DS BZGJ9 Fd I217W, I221W 764 DSCav1BZGJ9pi I217W, Inter-DS BZGJ9 Fd I217W, I221W, L78F 765 I221W, L78FDSCav1 GSJscINT_1 SC RSV F DSCAV1 Fd F2 linked to full 766fusion peptide by (Gly) n linker GSJscINT_2 SC RSV F DSCAV2 FdF2 linked to full 767 fusion peptide by (Gly) n linker GSJscINT_3SC RSV F DSCAV3 Fd F2 linked to full 768 fusion peptide by(Gly) n linker GSJscINT_2 F488W SC RSV F DSCAV4 Fd F2 linked to full 769fusion peptide by (Gly) n linker GSJscINT_1 Q354A SC RSV F DSCAV5 FdF2 linked to full 770 fusion peptide by (Gly) n linker GSJscINT_MBESC RSV F DSCAV6 Fd F2 linked to full 771 fusion peptide by(Gly) n linker GSJscINT_2 F488Wsh SC RSV F DSCAV7 Fd F2 linked to full772 fusion peptide by (Gly) n linker GSJscINT_1 F488Wsh SC RSV F DSCAV8Fd F2 linked to full 773 fusion peptide by (Gly) n linker BZGJ9-11SC BZGJ9-DS-Cav1 Fd GS linker between 102 774 w/IL to 145 BZGJ9-12SC BZGJ9-DS-Cav1 Fd GS linker between 101 775 w/ IL to 145 BZGJ9-13SC BZGJ9-DS-Cav1 Fd GS linker between 100 776 w/IL to 145 BZGJ9-14SC BZGJ9-DS-Cav1 Fd GS linker between 99 777 w/IL to 145 BZGJ9-15SC BZGJ9-DS-Cav1 Fd GS linker between 98 778 w/IL to 145 BZGJ9-16SC BZGJ9-DS-Cav1 Fd GS linker between 97 779 w/IL to 145 BZGJ9-17SC BZGJ9-DS-Cav1 Fd GGSG (SEQ ID NO: 780 w/IL 1443) linker between103 to 145 BZGJ9-18 SC BZGJ9-DS-Cav1 Fd GGSGG (SEQ ID NO: 781 w/IL1448) linker between 103 to 145 BZGJ9-19 SC BZGJ9-DS-Cav1 FdGGSGGSG (SEQ ID NO: 782 W/IL 1445) linker between 103 to 145 BZGJ9-20SC BZGJ9-DS-Cav1 Fd GGSGN (Res. 104-108 783 W/IL of SEQ ID NO:783) linker between 103 to 145 BZGJ9-21 SC BZGJ9-DS-Cav1 FdN linker between 102 784 W/IL to 145 BZGJ9-22 SC BZGJ9-DS-Cav1 FdISSTSATGS (Res. 97- 785 w/IL 105 of SEQ ID NO: 785) linker between96 to 145 BZGJ9-23 SC BZGJ9-DS-Cav1 Fd VTSTSATGS (Res. 97- 786 w/IL105 of SEQ ID NO: 786) linker between 96 to 145 BZGJ9-24SC BZGJ9-DS-Cav1 Fd NSALSATGS (Res. 97- 787 w/IL 105 of SEQ ID NO:787) linker between 96 to 145 BZGJ9-25 SC BZGJ9-DS-Cav1 FdISSTTSTGS (Res. 97- 788 w/IL 105 of SEQ ID NO: 788) linker between96 to 145 BZGJ9-26 SC BZGJ9-DS-Cav1 Fd VTSTTSTGS (Res. 97- 789 w/IL105 of SEQ ID NO: 789) linker between 96 to 145 BZGJ9-27SC BZGJ9-DS-Cav1 Fd NSALSSTGS (Res. 97- 790 W/IL 105 of SEQ ID NO:790) linker between 96 to 145 BZGJ9-28 SC BZGJ9-DS-Cav1 FdISSTSATVGGS (Res. 97- 791 w/IL 107 of SEQ ID NO: 791) linker between 96to 145 BZGJ9-29 SC BZGJ9-DS-Cav1 Fd VTSTSATTGGS (Res. 97- 792 w/IL107 of SEQ ID NO: 792) linker between 96 to 145 BZGJ9-30SC BZGJ9-DS-Cav1 Fd NSALSATGGS (Res. 97- 793 w/IL 106 of SEQ ID NO:793) linker between 96 to 145 BZGJ9-31 SC BZGJ9-DS-Cav1 FdLISSTTSTVGGS (Res. 794 w/IL 97-108 of SEQ ID NO: 794) linker between 96to 145 BZGJ9-32 SC BZGJ9-DS-Cav1 Fd VTSTTSTTGGS (Res. 97- 795 W/IL107 of SEQ ID NO: 795) linker between 96 to 145 BZGJ9-33SC BZGJ9-DS-Cav1 Fd NSALSSTGGS (Res. 97- 796 W/IL 106 of SEQ ID NO:796) linker between 96 to 145 Lumazine Synthase ParticlesBZGJ10-DSCav1-LS Monomer RSV F SC LS SEKS Furin site I and 797 on LSSEKSGS Furin site II (Res. 131-134, 131- 136 of SEQ ID NO: 797)BZGJ10-DSCav1 DEF-LS Monomer RSV F SC LS SEKS Furin site I and 798 on LSSEKSGS Furin site II (Res. 131-134, 131- 136 of SEQ ID NO: 797)BZGJ11-DSCav1-LS Monomer RSV F SC LS SEKS Furin site I and 799 on LSSEKSGS Furin site II (Res. 131-134, 131- 136 of SEQ ID NO: 797)BZGJ11-DSCav1-SS-LS Monomer RSV F SC LS SEKS Furin site I and 800 on LSSEKSGS Furin site II (Res. 131-134, 131- 136 of SEQ ID NO: 797)Non-cleavable Foldon, with Pep27 A2-PP1 SC w/o furin FdSEKS Furin site I and 801 sites to maintain SEKSGS Furin site pep27II (Res. 131-134, 131- 136 of SEQ ID NO: 797) B18537-PP1 SC w/o furin FdSEKS Furin site I and 802 sites to maintain SEKSGS Furin site pep27II (Res. 131-134, 131- 136 of SEQ ID NO: 797) A2-DS-Cav1-PP1SC w/o furin Fd SEKS Furin site I and 803 sites to maintainSEKSGS Furin site pep27 II (Res. 131-134, 131- 136 of SEQ ID NO: 797)B18537 DS-Cav1-PP1 SC w/o furin Fd SEKS Furin site I and 804sites to maintain SEKSGS Furin site pep27 II (Res. 131-134, 131-136 of SEQ ID NO: 797) A2-DS-Cav1-PP1-dFold SC w/o furin FdSEKS Furin site I and 805 sites to maintain SEKSGS Furin site pep27II (Res. 131-134, 131- 136 of SEQ ID NO: 797) B18537 DS-Cav1-PP1-SC w/o furin Fd SEKS Furin site I and 806 dFold sites to maintainSEKSGS Furin site pep27 II (Res. 131-134, 131- 136 of SEQ ID NO: 797)A2-DS-Cav1-PP1-GCN4 SC w/o furin Fd SEKS Furin site I and 807sites to maintain SEKSGS Furin site pep27 II (Res. 131-134, 131-136 of SEQ ID NO: 797) B18537 DS-Cav1-PP1- SC w/o furin FdSEKS Furin site I and 808 GCN4 sites to maintain SEKSGS Furin site pep27II (Res. 131-134, 131- 136 of SEQ ID NO: 797) BZGJ9-dscav1 N155QSC BZGJ9-DS-Cav1 Fd Removal of introduced 809 W/IL glycan site on BZGJ9-DS-Cav1 (SEQ ID:669 located in the linker region on Asn 105BZGJ9-DS-Cav1- Add Histidines to Fd Introduction of six 810 FerritinHisFerr to improve His residues to the expression and Ferritin molecule topurification enable purification of RSV F molecules inthe Ferritin context without using His-tag or Strep-Tag sequences.Additional constructs B18537-BZGJ9-9 B18537 strain Fd Single chain RSV F811 subtype B (strain B18537) with direct fusion of residue 103 to 145B18537-BZGJ9-10 B18537 strain Fd Single chain RSV F 812subtype B (strain B18537) with GS linker between residue 103 to 145B1-BZGJ9-9 B1 strain Fd Single chain RSV F 813 subtype B (strain B1)with direct fusion of residue 103 to 145 B1-BZGJ9-10 B1 strain FdSingle chain RSV F 814 subtype B (strain B) with GS linkerbetween residue 103 to 145 BZGJ9ext-9 xFd Single chain RSV F 815DS-Cav1 (BZGJ9 #669) with direct fusion of residue 103 to 145 and anelongation of the C- terminus adding residues hnvnagkstt(residues 473-482 of SEQ ID NO: 815) after L513 and prior to theThrombin-His-Strep tags. BZGJ9ext-10 xFd Single chain RSV F 816DS-Cav1 (BZGJ9 #669) with GS linker between residue 103 to 145 and anelongation of the C- terminus adding residues hnvnagkstt(residues 473-482 of SEQ ID NO: 815) after L513 and prior to theThrombin-His-Strep tags. B18537-BZGJ9ext-9 B18537 strain xFdSingle chain RSV F 817 DS-Cav1 (subtype B (strain B18537) withdirect fusion of residue 103 to 145 and an elongation ofthe C-terminus adding residues hnvnagkstt (residues 473-482 ofSEQ ID NO: 815) after L513 and prior to the Thrombin-His-Strep tags.B18537-BZGJ9ext-10 B18537 strain xFd Single chain RSV F 818DS-Cav1 (subtype B (strain B18537) with GS linker betweenresidue 103 to 145 and an elongation of the C-terminus addingresidues hnvnagkstt (residues 473-482 of SEQ ID NO: 815) afterL513 and prior to the Thrombin-His-Strep tags. B1-BZGJ9ext-9 B1 strainxFd Single chain RSV F 819 DS-Cav1 (subtype B (strain B1) withdirect fusion of residue 103 to 145 and an elongation ofthe C-terminus adding residues hnvnagkstt (residues 473-482 ofSEQ ID NO: 815) after L513 and prior to the Thrombin-His-Strep tags.B1-BZGJ9ext-10 B1 strain xFd Single chain RSV F 820 DS-Cav1 (subtype B(strain B1) with GS linker between residue 103 to 145and an elongation of the C-terminus adding residues hnvnagkstt(residues 473-482 of SEQ ID NO: 815) after L513 and prior to theThrombin-His-Strep tags. BZGJ9extxFd-9 Single chain RSV F 821DS-Cav1 (BZGJ9 # 669) with direct fusion of residue 103 to 145 and anelongation of the C- terminus adding residues hnvnagkstt(residues 473-482 of SEQ ID NO: 815) after L513 and prior to thecleavable Foldon and Thrombin-His-Strep tags. BZGJ9extxFd-10Single chain RSV F 822 DS-Cav1 (BZGJ9 #669) with GS linkerbetween residue 103 to 145 and an elongation of the C- terminus addingresidues hnvnagkstt (residues 473-482 of SEQ ID NO: 815) afterL513 and prior to the cleavable Foldon and Thrombin-His-Strep tags.B18537-BZGJ9extxFd-9 B18537 strain Single chain RSV F 823DS-Cav1 (subtype B (strain B18537) with direct fusion ofresidue 103 to 145 and an elongation of the C-terminus addingresidues hnvnagkstt (residues 473-482 of SEQ ID NO: 815) afterL513 and prior to the cleavable Foldon and Thrombin-His-Strep tags.B18537-BZGJ9extxFd- B18537 strain Single chain RSV F 824 10DS-Cav1 (subtype B (strain B18537) with GS linker betweenresidue 103 to 145 and an elongation of the C-terminus addingresidues hnvnagkstt (residues 473-482 of SEQ ID NO: 815) afterL513 and prior to the cleavable Foldon and Thrombin-His-Strep tags.B1-BZGJ9extxFd-9 B1 strain Single chain RSV F 825 DS-Cav1 (subtype B(strain B1) with direct fusion of residue 103 to 145and an elongation of the C-terminus adding residues hnvnagkstt(residues 473-482 of SEQ ID NO: 815) after L513 and prior to thecleavable Foldon and Thrombin-His-Strep tags. B1-BZGJ9extxFd-10B1 strain Single chain RSV F 826 DS-Cav1 (subtype B (strain B1) with GSlinker between residue 103 to 145 and an elongation ofthe C-terminus adding residues hnvnagkstt (residues 473-482 ofSEQ ID NO: 815) after L513 and prior to the Thrombin-His-Strep tags.BZGJ9-CS1 Single chain RSV F 1474 with linker MTSVLHRFDTDAF (Res.72-84 of SEQ ID NO: 1474) between 96 and 150 BZGJ9-CS2Single chain RSV F 1475 with linker MTSVLWFGDTDAFA (Res.72-84 of SEQ ID NO: 1475) between 96 and 150 BZGJ9-10- xFdSingle chain RSV F 1476 GSJCCtai15xFd based on sequence#707 with C-terminal sequence CChnvnagksttnGGLVPRGS (Res. 512-532 of SEQID NO: 834) encoding disulphide bonds and cleavable foldon BZGJ9-10- xFdSingle chain RSV F 1477 GSJCCtail6xFd based on sequence#707 with C-terminal sequence LLhnvnaCCsttnGGLVPRGS (Res. 512-532 of SEQID NO: 845) encoding disulphide bonds and cleavable foldon BZGJ9-10- xFdSingle chain RSV F 1478 GSJCCtail9xFd based on sequence#707 with C-terminal sequence CChnvnaCCsttnGGLVPRGS (Residues 512-532 ofSEQ ID NO: 851) encoding disulphide bonds and cleavable foldonBZGJ9-9-DS-Cav1- RSV F single chain 827 Ferritin BZGJ9-9 (#706) withFusion of residue 103 to 145in the Ferritin context BZGJ9-10-DS-Cav1-RSV F single chain 828 Ferritin BZGJ9-10 (#707) GS linker betweenresidue 103 to 145 BZGJ9-DS-Cav1- RSV F single chain 1429LongLink-Ferritin BZGJ9 (#669) in the Ferritin context witha long linker from the RSV F C-terminus to the Ferritin N- terminusBZGJ9-9-DS-Cav1- RSV F single chain 1430 LongLink-FerritinBZGJ9-9 (#706) with Fusion of residue 103 to 145 in theFerritin context with a long linker from RSV C-terminus toFerritin N-terminus BZGJ9-10-DS-Cav1- RSV F single chain 1431LongLink-Ferritin BZGJ9-10 (#707) GS linker between residue 103 to 145in the Ferritin context with a long linker from RSV C-terminus to Ferritin N-terminus BZGJ9-DS-Cav1- Add Histidines to RSV F1432 LongLinkFerritinHis Ferr to improve single chain expression andBZGJ9 (#669) in the purification Ferritin context witha long linker from the RSV F C-terminus to the Ferritin N-terminus with added histidines to the Ferritin molecule to facilitatepurification of Ferritin nanoparticles without the use of His orStrep-tags. BZGJ9-IG1 SC BZGJ9-DS-Cav1 ARLLGSGSG Res. 97-105 1433 w/ILof SEQ ID NO: 1433) linker from 96 to 147 BZGJ9-IG2 SC BZGJ9-DS-Cav1ARLLGGSG (Res. 97-105 1434 w/IL of SEQ ID NO: 1434)linker from 96 to 147 BZGJ9-IG3 SC BZGJ9-DS-Cav1 ARLLGGSG (Res. 97-1051435 w/IL of SEQ ID NO: 1435) linker from 96 to 148 BZGJ9-IG4SC BZGJ9-DS-Cav1 LARLLGSG (Res. 97-105 1436 w/IL of SEQ ID NO: 1436)linker from 96 to 147 BZGJ9-IG5 SC BZGJ9-DS-Cav1 mqstGGSG (Res. 97-1051437 w/IL of SEQ ID NO: 1437) linker from 96 to 147 BZGJ9-IG6SC BZGJ9-DS-Cav1 aqstGGSG (Res. 97-105 1438 w/IL of SEQ ID NO: 1438)linker from 96 to 147 B18537-BZGJ9-9- B18537 strain RSV F single chain1439 LongLink-Ferritin BZGJ9-9 (#811) with Fusion of residue 103to 145 in the Ferritin context with a long linker from RSV C-terminus toFerritin N-terminus B18537-BZGJ9-10- B18537 strain RSV F single chain1440 LongLink-Ferritin BZGJ9-10 (#812) GS linker betweenresidue 103 to 145 in the Ferritin context with a longlinker from RSV C- terminus to Ferritin N-terminus B1-BZGJ9-9-LongLink-B1 strain RSV F single chain 144 Ferritin BZGJ9-9 (#813) withFusion of residue 103 to 145 in the Ferritin context witha long linker from RSV C-terminus to Ferritin N-terminus B1-BZGJ9-10-B1 strain RSV F single chain 1442 LongLink-Ferritin BZGJ9-10 (#814) GSlinker between residue 103 to 145 in the Ferritin context with a longlinker from RSV C- terminus to Ferritin N-terminusThe yield of protein was calculated for several of the recombinant Fproteins, and is shown below in Table 27.

TABLE 27 Yield of recombinant RSV F protein expression Construct NameYield (mg/L) SEQ ID NO scRSVF9aCCextxFd 12.7 708 scRSVF9aC485C494xFd 4.1709 scRSVF9aC419C420extxFd 11.4 710 scRSVF9aC99C362xFd 2.2 711 scRSV F9axFd 15.7 715 scRSV F 9aextxFd 29.6 716 GSJscINT_1 0.84 766 GSJscINT_30.9 768

Example 11 The Structure of an RSV F Protein from the B18537 Strain withthe DSCav1 Mutations

This examples illustrated the similarity of the RSV protein with thestabilizing DSCav1 substitutions across RSV subtypes. The DSCav1substitutions were introduced into the RSV F protein from the B18537strain. And the three dimensional structure of the resulting recombinantprotein, including a C-terminal Foldon domain, was solved using methodssimilar to those described above. As shown in FIGS. 59-62 , the DSCav1substitutions could be successfully introduced into a RSV F glycoproteinB subtype to stabilize antigenic site Ø to generate a DSCav1 mutant onthe subtype B background that specifically binds to prefusion specificantibodies. Table 25, below, provides a summary of the crystallographicdata for DSCav1 on RSV F subtype B.

TABLE 25 Crystallographic data concerning DSCav1 subtype B RSV B18537 FPDB accession code Data collection Space group P4₁32 Cell constants a,b, c (Å) 167.9, 167.9, 167.9 a, b, g (°) 90, 90, 90 Wavelength (Å) 1.00Resolution (Å) 50.0-1.94 (2.01-1.94) R_(merge)   10 (78.8) I/sI 11.96(1.12)  Completeness (%) 95.9 (79.7) Redundancy 4.0 (2.4) RefinementResolution (Å) 1.94 Unique reflections 57,616 R_(work)/R_(free) (%)18.71/21.52 No. atoms Protein 3552 Ligand/ion 5 Water 401 B-factors (Å²)Protein 46.2 Ligand/ion 78.3 Water 53.2 R.m.s. deviations Bond lengths(Å) 0.009 Bond angles (°) 1.17 Ramachandran Favored regions (%) 96.18Allowed regions (%) 3.82 Disallowed regions (%) 0

Example 12 Design and Production of Recombinant RSV F Proteins without aTrimerization Domain

This example illustrated the design and production of recombinant RSV Fproteins that are stabilized in a prefusion conformation but which donot include a C-terminal trimerization domain to maintain stability ofthe membrane proximal lobe of the RSV F protein.

Briefly, in place of the C-terminal trimerization domain, a ring ofdisulfide bonds is introduced into the C-terminus of the F1 polypeptideby substituting cysteine residues for amino acids of the (10 helix. Thethree (10 helixes of the RSV F Ectodomain for a coil-coil thatstabilized the membrane proximal portion of the protein. When expressedin cells, inter-protomer disulfide bonds form between the cysteinesintroduced into the α10 helix, thereby “locking” the three (10 helix'sin close proximity and preventing movement of the membrane proximaldomain from the pre- to the post-fusion conformation. The (10 helix ofthe RSV F protein includes residues 492 to the transmembrane domain(residue 529).

In this example, the recombinant RSV F protein with the stabilizingcysteine ring is initially expressed as a recombinant protein thatincludes a trimerization domain. The trimerization domain can beproteolytically removed following initial expression. The cleavage canbe performed before, after, or during purification of the RSV F protein.Currently we purify the RSV F protein using tendem Ni2+ IMAC andStreptactin immobilization steps via the C-terminal His6 and StrepIItag, followed by thrombin digestion at room temperature for 12 hoursthen separation of the foldon from the RSV F protein by size-exclusionchromatography. It would be possible to also purify the cleaved RSV Fprotein by ion exchange.

FIGS. 63-68 show gel filtration results and coommassie blue staining ofreduced and non-reduced PAGE analysis of several of the recombinant Fproteins without trimerization domain as designed listed below. Table 22provides antigenic and physical characteristics of the indicatedconstructs, which include the DSCav1 substitutions, and cysteinesubstitutions in the α10 helix at positions 525 and 526 (CCTail4xFd),512 and 513 (CCTail5xFd), 519 and 520 (CCTail6xFd), and 512 and 512(CCLongxFd). The corresponding SEQ ID NO for each construct is shown inFIG. 66 .

TABLE 22 Antigenic and physical characteristics of engineered RSV Fglycoprotein variants. Physical characterization (Fractional D25reactivity) 1 hour incubation Osmolality 10 times Temp (°) pH (mM)Freeze- Construct 50 70 3.5 10 10 3000 thaw GSJ CCtail 4 × Fd Uncleaved0.9 0.5 0.9 0.9 1.0 .08 0.3 GSJ CC tail 4 × Fd Cleaved 0.9 0.4 0.9 1.01.0 0.7 0.4 GSJ CC tail 5 × Fd Uncleaved 0.9 0.6 0.9 1.0 1.0 0.7 0.2 GSJCC tail 5 × Fd Cleaved 0.9 0.2 0.9 1.0 1.0 1.0 0.2 GSJ CCtail 6 × FdUncleaved 0.9 0.4 0.9 0.9 1.0 0.7 0.2 GSJ CC tail6 × Fd Cleaved 1.0 0.30.9 0.9 1.0 0.7 0.3 GSJ CC tail Long × Fd Unleaved 0.9 0.1 0.7 0.8 0.80.6 0.1 GSJ CC tail Long × Fd Cleaved 1.0 0.3 0.9 1.0 1.0 0.8 0.2

Several RSV F protein sequences without trimerization domains, or with acleavable trimerization domain are provided in the SEQ ID NOs listed inTable 23, as well as an indication of design approach. The name, α10cysteine ring, presence or absence of C-terminal Foldon or cleavableFoldon, background sequence (e.g., “DSCAV1” indicates that the constructincludes the DSCav1 substitutions), the design concept, andcorresponding SEQ ID NO are indicated. In Table 23, the followingacronyms are used: DSCAV1: S155C, S290C, S190F, V207L substitutions;Op—Optimized coil coil; OpCC—Optimized Coil Coil with disulfides;InterC—Interprotomer disulfide at C-terminal helix;Multi-InterC—Multiple interprotomer disulfide stabilization; ECC:Enhanced coil-coil stability; FP-CC: Fusion peptide Cys bridge; 190P:190 pocket alternative amino acid; Fd (non-cleavable Foldon), xFd(cleavable foldon), N (no Foldon); CFM: Cavity Filling mutation; ICFM:Interface cavity filling mutations

The recombinant RSV F proteins with no or with a cleavable trimerizationdomain listed in Table 23 were expressed in cells under conditions wherethe proteins are secreted from the cells in the cell media as describedabove in Example 9. Each construct contains a leader sequence thatcauses the protein to enter the secretory system and be secreted. Themedium was then centrifuged and the supernatant used for antigenicitytesting for binding to the Site Ø specific antibody D25 and the Site IIspecific antibody Motavizumab (“Mota”, FIGS. 69A-69E). The conditionstested include D25 and Mota binding on day 0 (conditions 1 and 2), D25and Mota binding on day 0 after incubation at 70° C. for one hour(conditions 3 and 4), and D25 and Mota binding after 1 week at 4° C.(conditions 5 and 6). The control is the DSCav1 construct with a foldondomain. Specific antigenicity data for each construct is provided inFIGS. 69A-69E (the conditions tested are noted in the header rows).

TABLE 23Recombinant RSV F proteins that lack a trimerization domain, or that have a protease cleavabletrimerization domain. SEQ C- ID Construct Name Motif Term BackgroundDesign concept NO CS/GSJ ext2Opti1 512LLhnvnagLstVnimLttVI N DSCAV1 Op829 CS/GSJ ext2Opti2 512LLhnvnagLstVnKmLttVI N DSCAV1 Op 830CS/GSJ ext2Opti3 512LLhnvnKkLstVnKmLttVI N DSCAV1 Op 831 CS/GSJ512CChnvnagLstVnKmLttVI N DSCAV1 OpCC 832 ext2OpCC1 CS/GSJ512LLhnvnaCCstVnKmLttVI N DSCAV1 OpCC 833 ext2OpCC2 CS/GSJ512LLhnvnagLstVnKCCttVI N DSCAV1 OpCC 834 ext2OpCC3 CS/GSJ512FQNAVESTINTLQTTLEAV N DSCAV1 Op 835 ext2OpCC4 AQAI CS/GSJ GCN4cc1512IEDKIEEILSKQYHIENEIA N DSCAV1 OpCC 836 RCC CS/GSJ GCN4cc2512CCDKIEEILSKQYHIENEIA N DSCAV1 OpCC 837 RIK CS/GSJ CartOp512LLhnvnagLstVnKmLttVIKcc N DSCAV1 OpCC 838 GSJ CClongxFd512CCHNVNAGKSGG xFd DSCAV1 InterC 839 GSJ CCtail1xFd512CChnvnagksttnimitt xFd DSCAV1 InterC 840 GSJ CCtail2xFd512LLhnvnaCCsttnimitt xFd DSCAV1 InterC 841 GSJ CCtail3xFd512LLhnvnagksttniCCtt xFd DSCAV1 InterC 842 GSJ CCtail4xFd512LLhnvnagksttnCCitt xFd DSCAV1 InterC 843 GSJ CCtail5xFd512CChnvnagksttn xFd DSCAV1 InterC 844 GSJ CCtail6xFd 512LLhnvnaCCsttnxFd DSCAV1 InterC 845 GSJ CCtail7xFd 512LLhnvnagksttn xFd DSCAV1Extended C- 846 terminal helix GSJ CCtail8xFd 512LLhnvnagksttnimitt xFdDSCAV1 Extended C- 847 terminal helix GSJ CCtail9.1xFd512CChnvnaCCsttnimitt xFd DSCAV1 Multi-InterC 848 GSJ CCtail9xFd512CChnvnaCCsttn xFd DSCAV1 Multi-InterC 849 GSJ CCtail10xFd485C494C 512Cchnvnagksttn xFd DSCAV1 Multi-InterC 850 GSJ CCtail11xFd485C494C 512CchnvnaCCsttn xFd DSCAV1 Multi-InterC 851 Tail11SeqID 566 + 485C494C xFd SeqID 566 Multi-InterC 852 s_ds_F505W_oxFd512CchnvnaCCsttn (Based on DSCav1) GSJ CCtail12xFd 512CChnvnaCCsttniCCttxFd DSCAV1 Multi-InterC 853 GSJ CCtail13xFd 485C494C xFd DSCAV1Multi-InterC 854 512CchnvnaCCsttniCCtt GSJ CCtail14xFdSeqID 566 + 485C494C xFd SeqID 566 Multi-InterC 855512CchnvnaCCsttniCCtt (Based on DSCav1) GSJ CCtail15xFdSeqID 566 + 485C494C xFd SeqID 566 Multi-InterC 856 512CchnvnaCCsttn(Based on DSCav1) GSJ CCtail16xFd SeqID 566 + 485C494C xFd SeqID 566Multi-InterC 857 512CchnvnaGKsttniCCtt (Based on DSCav1) GSJT11DSCav1-S509W, L512C, L513C N DSCAV1 ECC 858 GSJT12DSCav1-S509F, L512C, L513C N DSCAV1 ECC 859 GSJT13DSCav1-L512F, L513C, 514E, N DSCAV1 ECC 860 515C GSJT14DSCav1-S509W, L513C, 514E, N DSCAV1 ECC 861 515C GSJT15DSCav1-S509F, L513C, 514E, N DSCAV1 ECC 862 515C GSJT16DSCav1-S509W, L512F, L513C, N DSCAV1 ECC 863 514E, 515C GSJT17DSCav1-L512F, L513C, 514E, N DSCAV1 ECC 864 515E, 516C GSJT18DSCav1-S509W, L513C, 514E, N DSCAV1 ECC 865 515E, 516C GSJT19DSCav1-S509F, L513C, 514E, N DSCAV1 ECC 866 515E, 516C GSJT20DSCav1-S509W, L512F, L513C, N DSCAV1 ECC 867 514E, 515E, 516C GSJT21DSCav1-L512C, L513E, 514C N DSCAV1 ECC 868 GSJT22DSCav1-L512C, L513E, 514E, N DSCAV1 ECC 869 516C GSJT23DSCav1-A515C, I516C N DSCAV1 ECC 870 GSJT24 DSCav1-L512T, L513E N DSCAV1ECC 871 GSJT25 DSCav1-L512T, L513E, A515C, N DSCAV1 ECC 872 I516C GSJT26DSCav1-L512S, L513E N DSCAV1 ECC 873 GSJT27 DSCav1-L512S, L513E, A515C,N DSCAV1 ECC 874 I516C GSJT28 DSCav1-L512S, L513D N DSCAV1 ECC 875GSJT29 DSCav1-L512S, L513D, A515C, N DSCAV1 ECC 876 I516C GSJT30DSCav1-L512F, A515C, I516C N DSCAV1 ECC 877 GSJT31DSCav1-L513F, A515C, I516C N DSCAV1 ECC 878 GSJT32DSCav1-L512F, L513F, A515C, N DSCAV1 ECC 879 I516C GSJT33DSCav1-L512Y, L513Y, N DSCAV1 ECC 880 A515C, I516C GSJT34DSCav1-L512F, L513Y, A515C, N DSCAV1 ECC 881 I516C GSJT35DSCav1-L512W, L513W, N DSCAV1 ECC 882 A515C, I516C GSJT36DSCav1-L5132W, L513Y, N DSCAV1 ECC 883 A515C, I516C GSJT37DSCav1-S509W, A515C, I516C N DSCAV1 ECC 884 GSJT38DSCav1-S509F, A515C, I516C N DSCAV1 ECC 885 GSJT39DSCav1-S509W, L512F, A515C, N DSCAV1 ECC 886 I516C GSJT40DSCav1-S509W, L512F, L513F, N DSCAV1 ECC 887 A515C, I516C GSJT41DSCav1-S509F, L512A, L513A, N DSCAV1 ECC 888 A515C, I516C GSJT42DSCav1-S509W, L512A, L513A, N DSCAV1 ECC 889 A515C, I516C GSJT43DSCav1-F505W, I506W, S509F, N DSCAV1 ECC 890 L512C, L513C GSJT44DSCav1-F505W, I506W, S509F, N DSCAV1 ECC 891 A515C, I516C GSJT45DSCav1-F505W, I506W, S509F, N DSCAV1 ECC 892 L512S, L513E, A515C, I516CGSJT46 DSCav1-F505W, I506W, S509F, N DSCAV1 ECC 893L512A, L513A, A515C, I516C GSJT47 DSCav1-F505K, I506D, S509F, N DSCAV1ECC 894 L512C, L513C GSJT48 DSCav1-F505K, I506D, S509F, N DSCAV1 ECC 895A515C, I516C GSJT49 DSCav1-F505K, I506D, L512C, N DSCAV1 ECC 896 L513CGSJT50 DSCav1-F505K, I506D, A515C, N DSCAV1 ECC 897 I516C GSJT51DSCav1-F505K, I506D, L512A, N DSCAV1 ECC 898 L513A, A515C, I516C GSJT52DSCav1-F505K, I506D, L512S, N DSCAV1 ECC 899 L513E, L512C, L513C GSJT53DSCav1-F505K, I506D, L512S, N DSCAV1 ECC 900 L513D, A515C, I516C GSJ-FP1DSCav1-F137C, R339C Fd DSCAV1 FP-CC 969 GSJ-FP2 DSCav1-F137C, T337C FdDSCAV1 FP-CC 970 GSJ-FP3 DSCav1-G139C, Q354C Fd DSCAV1 FP-CC 971 GSJ-FP4F137C, R339C Fd DSCAV1 FP-CC 972 GSJ-FP5 F137C, T337C Fd DSCAV1 FP-CC973 GSJ-FP6 G139C, Q354C Fd DSCAV1 FP-CC 974 GSJ-190P1 L260F Fd DSCAV1190P 975 GSJ-190P2 L260W Fd DSCAV1 190P 976 GSJ-190P3 L260Y Fd DSCAV1190P 977 GSJ-190P4 L260R Fd DSCAV1 190P 978 GSJ-190P5 L188F Fd DSCAV1190P 979 GSJ-190P6 L188W Fd DSCAV1 190P 980 GSJ-190P7 L188Y Fd DSCAV1190P 981 GSJ-190P8 L188R Fd DSCAV1 190P 982 GSJ-190P9 I57F Fd DSCAV1190P 983 GSJ-190P10 I57W Fd DSCAV1 190P 984 GSJ-190P11 I57R Fd DSCAV1190P 985 GSJ-190P12 L252F Fd DSCAV1 190P 986 GSJ-190P13 L252W Fd DSCAV1190P 987 GSJ-190P14 L252R Fd DSCAV1 190P 988 GSJ-190P15 V192F Fd DSCAV1190P 989 GSJ-190P16 V192W Fd DSCAV1 190P 990 GSJ-190P17 V192R Fd DSCAV1190P 991 GSJ-DS1 S150C, Y458C Fd DSCAV1 Stabilizing 992 DisulfidesGSJ-DS2 A149C, N460C Fd DSCAV1 Stabilizing 993 Disulfides GSJ-DS3S146C, N460C Fd DSCAV1 Stabilizing 994 Disulfides GSJ-DS4 A149C, Y458CFd DSCAV1 Stabilizing 995 Disulfides GJ-3-1 V220F Fd DSCAV1 CFM 996GJ-3-2 V220W Fd DSCAV1 CFM 997 GJ-3-3 V220M Fd DSCAV1 CFM 998 GJ-3-4T219F Fd DSCAV1 CFM 999 GJ-3-5 T219M Fd DSCAV1 CFM 1000 GJ-3-6 T219W FdDSCAV1 CFM 1001 GJ-3-7 T219R Fd DSCAV1 CFM 1002 GSJ-Int-FdF-1 I221F FdDSCAV1 ICFM 1003 GSJ-Int-FdF-2 I221Y Fd DSCAV1 ICFM 1004 GSJ-Int-FdF-3I221W Fd DSCAV1 ICFM 1005 GSJ-Int-FdF-4 Q224D, L78K Fd DSCAV1 ICFM 1006GSJ-Int-FdF-5 V278F Fd DSCAV1 ICFM 1007 GSJ-Int-FdF-6 Q279F Fd DSCAV1ICFM 1008 GSJ-Int-FdF-7 N277D, S99K Fd DSCAV1 ICFM 1009 GSJ-Int-FdF-8Q361F Fd DSCAV1 ICFM 1010 GSJ-Int-FdF-9 V402F Fd DSCAV1 ICFM 1011GSJ-Int-FdF-10 T400F Fd DSCAV1 ICFM 1012 GSJ-Int-FdF-11 T400W Fd DSCAV1ICFM 1013 GSJ-Int-FdF-12 H486F Fd DSCAV1 ICFM 1014 GSJ-Int-FdF-13 H486WFd DSCAV1 ICFM 1015 GSJ-Int-FdF-14 I217F Fd DSCAV1 ICFM 1016GSJ-Int-FdF-15 I217Y Fd DSCAV1 ICFM 1017 GSJ-Int-FdF-16 I217W Fd DSCAV1ICFM 1018 DSCav1OpFd1 F190V Fd DSCAV1 Enhanced 1019 stability of DSCav1DSCav1OpFd2 K226L Fd DSCAV1 Enhanced 1020 stability of DSCav1DSCav1OpFd3 T58I, A298M Fd DSCAV1 Enhanced 1021 stability of DSCav1DSCav1OpFd4 F190V, K226L Fd DSCAV1 Enhanced 1022 stability of DSCav1DSCav1OpFd5 F190V, T58I, A298M Fd DSCAV1 Enhanced 1023 stability ofDSCav1 DSCav1OpFd6 K226L, T58I, A298M Fd DSCAV1 Enhanced 1024stability of DSCav1 DSCav1OpFd7 T58I, A298M, F190V, K226L Fd DSCAV1Enhanced 1025 stability of DSCav1 CSGSJ1 xFd DSCAV1 Engineered alpha1456 10 coil coil with GCN4 internal motifs CSGSJ2 xFd DSCAV1Engineered alpha 1457 10 coil coil with GCN4 internal motifs CSGSJ3 xFdDSCAV1 Engineered alpha 1458 10 coil coil with GCN4 internal motifsCSGSJ4 xFd DSCAV1 Engineered alpha 1459 10 coil coil with GCN4 internalmotifs CSGSJ5 xFd DSCAV1 Engineered alpha 1460 10 coil coil withGCN4 internal motifs CSGSJ6 xFd DSCAV1 Engineered alpha 146110 coil coil with GCN4 internal motifs CSGSJ7 xFd DSCAV1Engineered alpha 1462 10 coil coil with GCN4 internal motifs BZGJ9-10-xFd DSCAV1 single chain F, 1463 TMCC1 alpha10 disulfide, Furinsite, Foldon, TM region BZGJ9-10-TMCC2 xFd DSCAV1 single chain F, 1464alpha10 disulfide, Furin site, Foldon, TM region GSJCCTail9- xFd DSCAV1F, alpha 10 1465 TMCC1 disulfide, Furin site, Foldon, TM regionGSJCCTail9- xFd DSCAV1 F, alpha10 1466 TMCC2 disulfide, Furinsite, Foldon, TM region GSJCCTail9- xFd DSCAV1 F, alpha10 1467 TMCC3disulfide, Furin site, TM region GSJCCTail9- xFd DSCAV1 F, alpha 10 1468TMCC4 disulfide, Furin site, TM regionThe yield of protein was calculated for several of the recombinant Fproteins, and is shown below in Table 26.

TABLE 26 Yield of recombinant RSV F protein expression Design Name Yieldmg/L SEQ ID NO CS/GSJ ext2OpCC1 0.39 832 CS/GSJ ext2OpCC2 0.33 833CS/GSJ ext2OpCC3 0.72 834 CS/GSJ ext2OpCC4 0.48 835 CS/GSJ GCN4cc1 2.85836 CS/GSJ GCN4cc2 0.75 837 CS/GSJ CartOp 0.36 838 GSJ CClongxFd 6.3 839GSJ CCtail1xFd 1.05 840 GSJ CCtail2xFd 0.33 841 GSJ CCtail3xFd 0.99 842GSJ CCtail4xFd 1.53 843 GSJ CCtail5xFd 2.13 844 GSJ CCtail6xFd 1.65 845CSGSJ7 0.66 1462 GSJ 1Cav1 13 8 913 JCB GSJ 4 8 942 JCB GSJ 5 8 943

Example 13 Additional Mutations to Stabilize the Membrane Distal Portionof the RSV F Ectodomain

This example illustrates additional mutations that were made to RSV F tostabilize the protein in its prefusion conformation.

Several RSV F protein sequences without trimerization domains weredesigned and are provided in the SEQ ID NOs listed in Table 24, as wellas an indication of design approach. The name, mutation relative to SEQID NO: 1026, presence or absence of C-terminal Foldon domain, backgroundsequence (e.g., “WT” indicates wild-type RSV F), the design concept, andcorresponding SEQ ID NO are indicated.

The recombinant RSV F proteins with a C-terminal trimerization domainlisted in Table 24 were expressed in cells under conditions where theproteins are secreted from the cells in the cell media. Each constructcontains a leader sequence that causes the protein to enter thesecretory system and be secreted as described above in Example 9. Themedium was then centrifuged and the supernatant used for antigenicitytesting for binding to the Site Ø specific antibody D25 and the Site IIspecific antibody Motavizumab (“Mota”, FIGS. 69A-69E). The conditionstested include D25 and Mota binding on day 0 (conditions 1 and 2), D25and Mota binding on day 0 after incubation at 70° C. for one hour(conditions 3 and 4), and D25 and Mota binding after 1 week at 4° C.(conditions 5 and 6). The control is the DSCav1 construct with a foldondomain. Specific antigenicity data for each construct is provided inFIGS. 69A-69E (the conditions tested are noted in the header rows).

TABLE 24 New stabilization with Foldon domain Mutation(s) relativeConstruct Name to SEQ ID NO: 1026 C-Term Background Design concept SEQID NO GSJ 1Cav1 1 S190W Fd WT S190 AA Scan 901 GSJ 1Cav1 2 S190L Fd WTS190 AA Scan 902 GSJ 1Cav1 3 S190R Fd WT S190 AA Scan 903 GSJ 1Cav1 4S190E Fd WT S190 AA Scan 904 GSJ 1Cav1 5 S190A Fd WT S190 AA Scan 905GSJ 1Cav1 6 S190Q Fd WT S190 AA Scan 906 GSJ 1Cav1 7 S190Y Fd WT S190 AAScan 907 GSJ 1Cav1 8 S190G Fd WT S190 AA Scan 908 GSJ 1Cav1 9 S190P FdWT S190 AA Scan 909 GSJ 1Cav1 10 S190I Fd WT S190 AA Scan 910 GSJ 1Cav111 S190T Fd WT S190 AA Scan 911 GSJ 1Cav1 12 S190C Fd WT S190 AA Scan912 GSJ 1Cav1 13 S190V Fd WT S190 AA Scan 913 GSJ 1Cav1 14 S190D Fd WTS190 AA Scan 914 GSJ 1Cav1 15 S190N Fd WT S190 AA Scan 915 GSJ 1Cav1 16S190H Fd WT S190 AA Scan 916 GSJ 1Cav1 17 S190K Fd WT S190 AA Scan 917GSJ 1Cav1 18 DS V207L Fd WT S190 AA Scan 918 GSJ 1Cav1 19 DS S190F Fd WTS190 AA Scan 919 GSJ 1Cav1 20 V207G Fd WT S190 AA Scan 920 GSJ 1Cav1 21V207A Fd WT S190 AA Scan 921 GSJ 1Cav1 22 V207S Fd WT S190 AA Scan 922GSJ 1Cav1 23 V207T Fd WT S190 AA Scan 923 GSJ 1Cav1 24 V207C Fd WT S190AA Scan 924 GSJ 1Cav1 25 V207L Fd WT S190 AA Scan 925 GSJ 1Cav1 26 V207IFd WT S190 AA Scan 926 GSJ 1Cav1 27 V207M Fd WT S190 AA Scan 927 GSJ1Cav1 28 V207P Fd WT S190 AA Scan 928 GSJ 1Cav1 29 V207F Fd WT S190 AAScan 929 GSJ 1Cav1 30 V207Y Fd WT S190 AA Scan 930 GSJ 1Cav1 31 V207W FdWT S190 AA Scan 931 GSJ 1Cav1 32 V207D Fd WT S190 AA Scan 932 GSJ 1Cav133 V207E Fd WT S190 AA Scan 933 GSJ 1Cav1 34 V207N Fd WT S190 AA Scan934 GSJ 1Cav1 35 V207Q Fd WT S190 AA Scan 935 GSJ 1Cav1 36 V207H Fd WTS190 AA Scan 936 GSJ 1Cav1 37 V207K Fd WT S190 AA Scan 937 GSJ 1Cav1 38V207R Fd WT S190 AA Scan 938 JCB GSJ 1 Y198F Fd WT Probing JCB16/18/24939 residues JCB GSJ 2 T219L Fd WT Probing JCB16/18/24 940 residues JCBGSJ 3 V296I Fd WT Probing JCB16/18/24 941 residues JCB GSJ 4 K226M Fd WTProbing JCB16/18/24 942 residues JCB GSJ 5 K226L Fd WT ProbingJCB16/18/24 943 residues IG1-V192M V192M Fd WT 944 IG2- A298M Fd WT 945A298M_RSVF(+)FdTHS-paH IG2-T58I_A298M T58I_A298M Fd WT 946 IG2- T58I,V192F, A298I Fd WT 947 T58I_V192F_A298I_RSVF(+)FdTHS- paH IG2- T58I,V192M, Fd WT 948 T58I_V192M_A298I_RSVF(+)FdTHS- A298I paH i167m-a298mI167M, A298M Fd WT 949 i167m-l181m I167M, L181M Fd WT 950 i199f I199F FdWT 951 i57c-s190c I57C, S190C Fd WT 952 ig2-t581-a298m T58L, A298M Fd WT953 ig2-t58m T58M Fd WT 954 ig2-t58m-a298i T58M, A298I Fd WT 955ig2-t58m-a298L T58M, A298L Fd WT 956 ig2-v192c-ins192-193-g-e256c V192C,G insertion Fd WT 957 192/193, E256C rsv f ths_s_f505w_o_s509fths_s_F505W_o_S509F N WT 958 rsv f ths_s_f505w_s509f ths_s_F505W_S509F NWT 959 t58i-a298i T58I, A298I Fd WT 960 t58m-a298m T58M, A298M Fd WT 961v1791-t189f V179L, T189F Fd WT 962 v192f V192F Fd WT 963 v192f-l252aV192F, L252A Fd WT 964 v56m-i167m-l181m V56M, I167M, Fd WT 965 L181Mv56m-i167m-v296m V56M, I167M, Fd WT 966 V296M v56m-l181f V56M, L181F FdWT 967 w52c-s150c W52C, S150C Fd WT 968

Example 14 Minimal Site Ø Immunogens

The site Ø epitope of RSV F is located on the apex of the trimer spikeand includes the region recognized by the three neutralizing antibodiesD25, AM22 and 5C4. More specifically, as delineated by the crystalstructure of the RSV F/D25 complex, this epitope comprises the outersurface of helix α4 (residues 196-210) and the adjacent loop (residues63-68) between 32 and α1. This example illustrates the design andcharacterization of antigens that present site Ø alone with minimaladjoining residues, and which can be used to elicit a site Ø immuneresponse and can be more cost effective to produce than full lengthpre-fusion stabilized RSV F trimer.

General Concepts for the Design of Minimal Site Ø RSV F Immunogens

The minimal site Ø immunogens were designed utilizing four primarydesign concepts: circular permutation, scaffolded circular permutation,domain III immunogens, and multimerization.

Circular permutations involve altering the native connections within aprotein structure while keeping the spatial orientation(s) of thecomponent parts. The minimal site Ø epitope components α4 and the β2-α1loop are each part of two separate loop segments within RSV F1. Tocreate stable site Ø folds, the two loop segments were connected(C-terminal to N-terminal) with short flexible amino acid linkers in thetwo different possible orders, thereby creating two separate folds, eachof which preserve the site Ø epitope (FIG. 70A).

To create scaffolded circular permutations, the short flexible linkersof circularly permutated site Ø proteins were replaced by small rigidsegments from other proteins that potentially provide greater stabilitythan simple amino acid linkers (FIG. 70B).

Domain III (residues 50-306) is a larger domain of approximately 250amino acids of the RSV F protein that contains the site Ø epitope (seeFIG. 70D). The domain III residues surrounding site Ø provides furtherstructural stability to site Ø while not adding significant additionaldistracting surface epitopes to the immunogen. Domain III contains anatural furin cleavage site between residues 136 and 137 which exposesthe fusion peptide. Domain III can be further stabilized by replacingthe cleavage site with an amino acid linker or by performing a circularpermutation to link the original N- and C-termini or domain III andcreate a new N- and C-termini at the cleavage site. Both of thesemethods were utilized to stabilize various domain III immunogens.

Lastly, site Ø immunogens were multimerized to enhance immunogenicity(FIGS. 70D and 70E). Trimerization was utilized to mimic the nativetrimer observed in the pre-fusion RSV F viral spike and larger definedoligomers such as 24mers and 60mers were utilized to specificallyenhance immunogenicity. The was accomplished by introducing disulfidebonds between constructs, or by covalently linking constructs togetheras dimers or trimers using amino acid linkers or by linking constructsto multimerization domains using amino acid linkers. Some constructsutilized a combination of these strategies. The smallest multimerizationdomains used were trimers (e.g. GCN4) and the largest were 60mers (e.g.lumazine synthase). We also used pentamers, 12mers and 24mers.

In addition to the major design concepts delineated above, theimmunogens were stabilized by using several other methods includingaddition of disulfide bonds, cavity filling mutations, reduction ofsurface hydrophobicity, addition of charged surface residues, andaddition of N-linked glycans and truncation of potentially flexibleregions. A listing of several minimal site Ø immunogens is provided inTables 20 (site Ø non-particle immunogens) and 21 (site Ø immunogens ona protein nanoparticle), as well as an indication of design approach.The name, concept, residues of RSV F protein, scaffold or other addedprotein, and corresponding SEQ ID NO are indicated. In Tables 20 and 21,the following acronyms are used: SØ: minimal Site Ø; CP: circularpermutation; DS: Disulfide; CAV: cavity filling; Charge: Adding chargedresidues; SC: single chain; TD3: tandem domain III domain; D3: domainIII; RH: Reduce Hydrophobicity; Fd: T4 Fd trimerization domain; CCMPTD:chicken cartilage matrix protein trimerization domain; MTQ-CC: MTQcoiled coil trimerization motif; CXVIII: Collagen XVIII trimerizationdomain; 2MOE: Miz-1 zinc finger 6 (2MOE) scaffold; ATCase: aspartatecarbamoyltransferase (ATCase) trimerization domain (1GQ3); GCN4: GCN4trimerization domain; Fer: Ferritin; Dps: Microbacterium ArborescensDps; LS: A. aeolicus Lumazine Synthase; Thr: thrombin; EH: exposedhydrophobic; HCP1: P. aeruginosa hcp1 (1y12).

The minimal site C immunogens were expressed in cells using a systemthat results in secretion of the minimal site C immunogens into thetissue culture medium as described above in Example 9. The medium wasthen centrifuged and the supernatant used for antigenicity testing forbinding to the Site C specific antibodies D25, AN22 and 5C4 by ELISA(FIGS. 72A-72F). The conditions tested include D25 binding after 0 and 1week at 4° C. (conditions 1 and 2), D25 binding after 1 hr. at 60° C.(condition 3), 70° C. (condition 4), 80° C. (condition 5), 90° C.(condition 6), or 100° C. (condition 7), AM22 binding after two weeks at4° C. (condition 8), 5C4 binding at week 0 4° C. (condition 9). Theaverage of D25, AM22, and D25 binding after 1 hour at 70° C. is alsoshown (condition 10). A summary of the antigenicity data is provided inFIG. 71 , which shows the number of site Ø immunogens that fall withineach design category and which produced an ELISA result of at least 1.5.Specific antigenicity data for each construct is provided in FIGS.72A-72F (the conditions tested are noted in the header rows). Theresults indicate that the minimal site Ø immunogens specifically bind toprefusion specific antibodies; and thus, are useful for inducing animmune response in a subject to antigenic site Ø. Additionally, theresults indicate that the minimal site Ø constructs can be used asprobes for isolating and detecting RSV F prefusion specific antibodiesfrom a sample.

Based on the antigenicity data, 14 of the initial constructs wereselected as representative for evaluation in animal models for producingan immune response, and for additional physical and structuralcharacterization. The metric for choosing the 14 included selectingconstructs showing average of ELISAs for D25 (week1), AM22 (week 2) andD25 after 1 hour at 70 degrees. To prevent several very similarconstructs being chosen for each category, each of the categories wassubdivided into further categories (SEQ ID NO in parentheses):

Cateuory 1: Monomers:

-   -   site Ø circular permutation: TZ-13 (354567-108) Avg: 3.18 (SEQ        ID NO: 1040)    -   site Ø circular permutation with scaffold: JG_2KN0 (354567-417)        Avg: 3.00 (SEQ ID NO: 1053)    -   domain III: E-CP_RBD51-307_14mutDS-Cav1_THS (354567-273) Avg:        3.17 (SEQ ID NO: 1156)    -   domain III dimer: GSJnh4-TWIN (354567-693) Avg: 3.06 (SEQ ID NO:        1194)

Category 2: Trimers:

-   -   site Ø circular permutations: TZ-19 (354567-126) Avg: 3.08 (SEQ        ID NO: 1106)    -   domain III (two are tied): RSVF(+)THS_s_to_hp2_foldon        (354567-210) Avg: 3.08 (SEQ ID NO: 1170), and MS_08 (354567-447)        Avg: 3.08 (SEQ ID NO: 1188)    -   domain III dimer: GSJnh4Fd-TWIN (354567-705) Avg: 3.01 (SEQ ID        NO: 1212)

Category 3: Multivalent Monomers:

-   -   site Ø circular permutation on ferritin: 2m0e-resurf1-Ferritin        (354567-621) Avg: 2.81 (SEQ ID NO: 1276)    -   domain III on ferritin: GSJnh2F (354567-471) Avg: 3.10 (SEQ ID        NO: 1220)    -   monomer on a non-ferritin oligomer:        LS1-E-CP_RBD51-307_11mutDS-Cav1THS (354567-315) Avg: 2.72 (SEQ        ID NO: 1281)    -   Additional: MP11 (354567-642) Avg: 3.05 (SEQ ID NO: 1263)

Category 4: Multivalent Trimers:

-   -   domain III on nanoparticles (2): GSJnh2Fd-F (354567-483) Avg:        2.57 (SEQ ID NO: 1266), and GSJnh4Fd-F (354567-489) Avg: 2.02        (SEQ ID NO: 1268)

TABLE 20 Minimal Site Ø immunogens (not on a protein nanoparticle)Region of RSVF scaffold or other added SEQ Name Concept (residue #s)protein ID NO Circular permutation of site Ø (26) JCB_01 CP-SØ + CAV60-94, 192-232 APGG linker (Seq_1454) 1027 JCB_02 CP-SØ + CAV60-94, 192-232 APGG (Seq_1454) linker, 1028 DS JCB_03 CP-SØ + CAV60-94, 192-232 APGG (Seq_1454) linker, 1029 DS JCB_04 CP-SØ + CAV60-94, 192-232 AGSG (Seq_1455) linker 1030 JCB_05 CP-SØ + CAV60-94, 192-232 AGSG (Seq_1455) linker, 1031 DS JCB_06 CP-SØ + CAV60-94, 192-232 AGSG (Seq_1455) linker, 1032 DS JCB_07 CP-SØ + CAV60-94, 192-229 GSG linker 1033 JCB_08 CP-SØ + CAV 60-94, 192-229GSG linker, DS 1034 JCB_09 CP-SØ + CAV 60-94, 192-229 GSG linker, DS1035 TZ-09 CP-SØ + DS + CAV +  192-242, 60-97 GGSGSGG (Seq_1446) linker1036 glycan TZ-10 CP-SØ + DS + CAV +  192-242, 60-97GGSGSGG (Seq_1446) linker 1037 charge TZ-11 shorter CP- 192-242, 60-97GGSGSGG (Seq_1446) linker 1038 SØ + DS + CAV + charge TZ-12CP-SØ + DS + CAV +  192-242, 60-97 GGSGSGG (Seq_1446) linker 1039 chargeTZ-13 CP-SØ + DS + CAV +  192-242, 60-97 GGSGSGG (Seq_1446) linker 1040glycan TZ-14 CP-SØ + DS + CAV +  192-242, 60-97GGSGSGG (Seq_1446) linker 1041 glycan RSVF ( + ) THS_ CP-SØ 62-69-Ggsggggsggsg (Seq_1447) 1042 me ggsggggsggsg linker (Seq_1447)- 196-212RSVF ( + ) THS_ CP-SØ 62-69- ggsggggsggsg (Seq_1447) 1043 me_hp1ggsggggsggsg linker (Seq_1447)- 196-212 RSVF ( + ) THS_ CP-SØ 62-69-ggsggggsggsg (Seq_1447) 1044 me_ds ggsggggsggsg linker (Seq_1447)-196-212 RSVF ( + ) THS_ CP-SØ 62-69- ggsggggsggsg (Seq_1447) 1045me_hp1_ds ggsggggsggsg linker (Seq_1447)- 196-212 JG_circ1 CP-SØ60-94, 193-237 GGSGG (Seq_1448) linker 1046 JG_circ1_ds CP-SØ + DS60-94, 193-237 GGSGG (Seq_1448) linker 1047 JG_circl_delKCP-SØ + deletion 60-94, 193-237 GGSGG (Seq_1448) linker 1048JG_circl_sol_ CP-SØ + DS 60-94, 193-237 GGSGG (Seq_1448) linker 1049 dsJG_circl_sol CP-SØ 60-94, 193-237 GGSGG (Seq_1448) linker 1050 JG_Circ2CP-SØ 60-75, 193-218 GGSGG (Seq_1448) linker 1051 JG_Circ2_sol CP-SØ60-75, 193-218 GGSGG (Seq_1448) linker 1052Circular permutation with scaffold connection (19) JG_2KN0CP-SØ + section of TENC1 60-75, 193-218 GGSGGSG (Seq_1445) 1053(2KNO) scaffold linker and TENC1 (2KNO) scaffold Site_0_2a90_CP-SØ + CAV + RH +  61-96, 192-235 WWE domain fragment 1054 1_GYCsection of 2A90 scaffold (2A90) Site_0_2a90_ CP- 61-96, 192-235WWE domain fragment 1055 2_GYC SØ + CAV + RH + DS +  (2A90)section of 2A90 scaffold Site_0_2a90_ CP- 61-96, 192-235WWE domain fragment 1056 3_GYC SØ + CAV + RH + DS +  (2A90)section of 2A90 scaffold Site_0_2w59_ CP-SO + CAV + RH +  60-96, 193-238IgY fragment (2W59) 1057 1_GYC section of 2W59 scaffold Site_0_2w59_ CP-60-96, 193-238 IgY fragment (2W59) 1058 2_GYC SØ + CAV + RH + DS + section of 2W59 scaffold Site_0_2w59_ CP- 60-96, 193-238IgY fragment (2W59) 1059 3_GYC SØ + CAV + RH + DS + section of 2W59 scaffold Site_0_3u2e_ CP-SØ + CAV + RH +  61-96, 192-238EAL domain fragment 1060 1_GYC section of 3U2E scaffold (3U2E)Site_0_3u2e_ CP- 61-96, 192-238 EAL domain fragment 1061 2_GYCSØ + CAV + RH + DS +  (3U2E) section of 3U2E scaffold Site_0_3u2e_ CP-61-96, 192-238 EAL domain fragment 1062 3_GYC SØ + CAV + RH + DS + (3U2E) section of 3U2E scaffold Site_0_2vj1_ CP-SO + CAV + RH + 61-96, 192-240 SARS proteinase fragment 1063 1_GYCsection of 2VJ1 scaffold (2VJ1) Site_0_2vj1_ CP- 61-96, 192-240SARS proteinase fragment 1064 2_GYC SØ + CAV + RH + DS +  (2VJ1)section of 2VJ1 scaffold Site_0_2vj1_ CP- 61-96, 192-240SARS proteinase fragment 1065 3_GYC SØ + CAV + RH + DS +  (2VJ1)section of 2VJ1 scaffold Site_0_1chd_ CP-SO + CAV + RH +  60-95, 192-240CheB methylesterase 1066 1_GYC section of 1CHD scaffold fragment (1CHD)Site_0_1chd_ CP- 60-95, 192-240 CheB methylesterase 1067 2_GYCSØ + CAV + RH + DS +  fragment (1CHD) section of 1CHD scaffoldSite_0_1chd_ CP- 60-95, 192-240 CheB methylesterase 1068 3_GYCSØ + CAV + RH + DS +  fragment (1CHD) section of 1CHD scaffoldSite_0_1pqz_ CP-SØ + CAV + RH +  60-96, 192-239 Immunomodulatory protein1069 1_GYC section of 1PQZ scaffold M144 fragment (1PQZ) Site_0_1pqz_CP- 60-96, 192-239 Immunomodulatory protein 1070 2_GYCSØ + CAV + RH + DS +  M144 fragment (1PQZ) section of 1PQZ scaffoldSite_0_1pqz_ CP- 60-96, 192-239 Immunomodulatory protein 1071 3_GYCSØ + CAV + RH + DS +  M144 fragment (1PQZ) section of 1PQZ scaffoldCircular permutation of site Ø with trimer (39) JCB_10CP-SØ + CAV + GCN4 60-94, 192-232 APGG linker, GCN4 1072 JCB_11CP-SØ + CAV + DS + GCN4 60-94, 192-232 APGG linker, GCN4 1073 JCB_12CP-SØ + CAV + DS + GCN4 60-94, 192-232 APGG linker, GCN4 1074 JCB_13CP-SØ + CAV + DS + GCN4 60-94, 192-232 APGG linker, GCN4 1075 JCB_14CP-SØ + CAV + DS + GCN4 60-94, 192-232 APGG linker, GCN4 1076 JCB_15CP-SØ + CAV + DS + GCN4 60-94, 192-232 APGG linker, GCN4 1077 JCB_16CP-SØ + CAV + GCN4 60-94, 192-229 GSG linker, GCN4 1078 JCB_17CP-SØ + CAV + DS + GCN4 60-94 192-229 GSG linker, DS, GCN4 1079 JCB_18CP-SØ + CAV + DS + GCN4 60-94 -229 GSG linker, DS, GCN4 1080 JCB_19CP-SØ + CAV + DS + GCN4 60-94, 192-229 GSG linker, GCN4 1081 JCB_20CP-SØ + CAV + DS + GCN4 60-94, 192-229 GSG linker, DS, GCN4 1082 JCB_21CP-SØ + CAV + DS + GCN4 60-94, 192-229 GSG linker, DS, GCN4 1083 TZ-01CP-SØ + interchain DS 192-242, 60-97 GGSGSGG (Seq_1446) linker 1084TZ-02 CP-SØ + interchain 192-242, 60-97 GGSGSGG (Seq_1446) linker 1085DS + CAV TZ-03 CP-SØ + interchain 192-242, 60-97GGSGSGG (Seq_1446) linker 1086 DS + CAV TZ-04 CP-SØ + interchain192-242, 60-97 GGSGSGG (Seq_1446) linker 1087 DS + CAV TZ-05CP-SØ + interchain 192-242, 60-97 GGSGSGG (Seq_1446) linker 1088DS +  CAV + charge TZ-06 CP-SØ + interchain 192-242, 60-97GGSGSGG (Seq_1446) linker 1099 DS + CAV + charge TZ-07CP-SØ + interchain 192-242, 60-97 GGSGSGG (Seq_1446) linker 1100DS + CAV + glycan TZ-08 CP-SØ + interchain 192-242, 60-97GGSGSGG (Seq_1446) linker 1101 DS + CAV + glycan TZ-15CP-SØ + DS + CXVIII 58-97, 192-242 GGSGSGSG (Seq_1449) linker, 1102CXVIII TZ-16 CP-SØ + DS + CAV +  58-97, 192-242 GGSGSGSG (Seq_1449) 1103CXVIII linker, CXVIII TZ-17 CP-SØ + DS + CAV +  58-97, 192-242GGSGSGSG (Seq_1449) 1104 CXVIII linker, CXVIII TZ-18 CP-SØ + DS + CAV + 58-97, 192-242 GGSGSGSG (Seq_1449) 1105 CXVIII linker, CXVIII TZ-19 CP-58-97, 192-242 GGSGSGSG (Seq_1449) 1106 SØ + DS + CAV + charge + linker, CXVIII glycan + CXVIII TZ-20 CP- 58-97, 192-242GGSGSGSG (Seq_1449) 1107 SØ + DS + CAV + charge +  linker, CXVIIIglycan + CXVIII AO_1 SC CP-SØ trimers 60-97, 194-239multiple glycine linkers 1108 AO_2 SC CP-SØ trimers 60-97, 194-239multiple glycine linkers 1109 AO_3 SC CP-SØ trimers 60-97, 194-239multiple glycine linkers 1110 AO_4 SC CP-SØ trimers 60-97, 194-239multiple glycine linkers 1111 AO_5 SC CP-SØ trimers 60-97, 194-239multiple glycine linkers 1112 AO_6 SC CP-SØ trimers 60-97, 194-239multiple glycine linkers 1113 AO_7 CP-SØ + N-terminal Fd 60-97, 194-239Glycine linkers and Fd 1114 AO_8 CP-SØ + C-terminal Fd 60-97, .94-239Glycine linkers and Fd 1115 AO_9 CP-SØ + C-terminal 60-97, 194-239E coli ATCase 1116 ATCase trimerization domain MP5 CP-SØ + Fd 56-97 GG-GG linker and Fd 1117 189-211 MP6 CP-SØ + Fd 56-97 G 189-GG linker and Fd 1118 211 MP7 CP-SØ + GCN4ization 56-97 GG 189-GG linker and 1119 domain 211 GCN4ization domain MP8 CP-SØ + C-terminal56-97 G- ATCase 1120 ATCase ATCAse-189-211Site Ø minimal epitope on a scaffold (6) 2m0e-resurf1 Minimal SØ on 2M0E2M0E 1121 2m0e-resurf2 Minimal SØ on 2M0E 2M0E 1122 2m0e-resurf3Minimal SØ on 2M0E 2M0E 1123 2M0E_r04 Minimal SØ on 2M0E 196-212 2M0E1124 2M0E_r05 Minimal SØ on 2M0E 196-212 2M0E 1125 2M0E_r06Minimal SØ on 2M0E 196-212 2M0E 1126 Domain III (42) RBD51-307D3 + DS + R H 51-307 1127 11mut DS- Cav1 RBD51-307 D3 + DS + RH, add51-307 1128 11mut DS- glycans Cav1 2sug RBD51-304 D3 + DS + RH, add51-304 1129 11mut DS- glycans Cav1 3sug RBD51-307 D3 + reduce 51-3071130 10mut DS- hydrophobicity Cav1 RBD51-307 D3 + RH, add glycans 51-3071131 10mut DS- Cav1 2sug RBD51-304 D3 + RH, add glycans 51-304 113210mut DS- Cav1 3sug CP RBD51-307 CP-D3 + DS, RH 51-307 1133 11mut DS-Cav1 CP RBD51-307 CP-D3 + DS, RH 51-307 1134 11mut DS- Cav1 2sugCP RBD51-304 CP-D3 + DS, RH 51-304 1135 11mut DS- Cav1 3sug CP RBD51-307CP-D3, RH 51-307 1136 10mut DS- Cav1 CP RBD51-307 CP-D3, RH, add glycans51-307 1137 10mut DS- Cav1 2sug CP RBD51-304 CP-D3, RH, add glycans51-304 1138 10mut DS- Cav1 3sug JCB_28 D3 + CAV 50-96, 149-306GSGGGSG (Seq_1450) linker 1139 JCB_29 D3 + CAV 50-96, 149-306GSGGGSG (Seq_1450) linker 1140 RSVF ( + ) THS_ CP-D3 + DS-Cav1 146-306-GGSGG (Seq_1448) linker 1141 s_to ggsgg (Seq_1448)- 50-105RSVF ( + ) THS_ CP-D3, RH + DS-Cav1 146-306- GGSGG (Seq_1448) linker1142 s_to_hp2 ggsgg (Seq_1448)- 50-105 RSVF ( + ) THS_CP-D3, RH + DS-Cav1 146-306- GGSGG (Seq_1448) linker 1143 s_to_hp12ggsgg (Seq_1448)- 50-105 RSVF ( + ) THS_ CP-D3, RH + DS-Cav1 146-306-GGSGG (Seq_1448) linker 1144 s_to_hp2_I221F ggsgg (Seq_1448)- 50-105RSVF ( + ) THS_ CP-D3, RH + DS-Cav1 146-306- GGSGG (Seq_1448) linker1145 s_to_hp2_ds ggsgg (Seq_1448)- 50-105 RSVF ( + ) THS_CP-D3, RH + DS-Cav1 146-306- GGSGG (Seq_1448) linker 1146 s_to_hp23ggsgg (Seq_1448)- 50-105 RSVF ( + ) THS_ CP-D3, RH + DS-Cav1 146-306-GGSGG (Seq_1448) linker 1147 s_to_hp123 ggsgg (Seq_1448)- 50-105RSVF ( + ) THS_ CP-D3 + DS-Cav1 146-306- GGSGG (Seq_1448) linker 1148s_to_A102C- ggsgg (Seq_1448)- A241C 50-105 RSVF ( + ) THS_CP-D3, RH + DS-Cav1 146-306- GGSGG (Seq_1448) linker 1149 s_to_hp2ggsgg (Seq_1448)- A102C-A241C 50-105 RSVF ( + ) THS_ CP-D3, RH + DS-Cav1146-306- GGSGG (Seq_1448) linker 1150 s_to_hp12 ggsgg (Seq_1448)-A102C-A241C 50-105 RSVF ( + ) THS_ CP-D3, RH + DS-Cav1 146-306-GGSGG (Seq_1448) linker 1151 s_to_hp2_I221F ggsgg (Seq_1448)-A102C-A241C 50-105 RSVF ( + ) THS_ CP-D3, RH + DS-Cav1 146-306-GGSGG (Seq_1448) linker 1152 s_to_hp2_ds ggsgg (Seq_1448)- A102C-A241C50-105 RSVF ( + ) THS_ CP-D3, RH + DS-Cav1 146-306-GGSGG (Seq_1448) linker 1153 s_to_hp23 ggsgg (Seq_1448)- A102C-A241C50-105 RSVF ( + ) THS_ CP-D3, RH + DS-Cav1 146-306-GGSGG (Seq_1448) linker 1154 s_to_hp123 ggsgg (Seq_1448)- A102C-A241C50-105 RSVF ( + ) THS_ CP-D3, RH + DS-Cav1 146-306-GGSGG (Seq_1448) linker 1155 s_to_hp1234 ggsgg (Seq_1448)- A102C-A241C50-105 E-CP_RBD51- CP-D3, RH + DS-Cav1 GG linker 1156 307_14mutDS-Cav1_THS E-RBD51- CP-D3, RH + DS-Cav1 1157 307_14mut_DS- Cav1_THSRSVF ( + ) THS_ CP-D3, RH + DS-Cav1 146-306- GGSGG (Seq_1448) linker1158 s_to_hp1234 ggsgg (Seq_1448)- A102C-A241C 50-105 K196C-E60CE-CP_RBD51- CP-D3, RH + DS-Cav1 GG linker 1159 307_14mutDS- Cav1_THSK196C-E60C E-RBD51- CP-D3, RH + DS-Cav1 1160 307_14mut_DS- Cav1_THSK196C-E60C E-CP_RBD51- CP-D3, RH + DS-Cav1 GG linker 1161 307_11mutDS-Cav1_THS E-RBD51- CP-D3, RH + DS-Cav1 1162 307_11mut_DS- Cav1_THSE-CP_RBD51- CP-D3, RH + DS-Cav1 GG linker 1163 307_11mut- K196C-E60C-DS-Cav1_THS E-RBD51- CP-D3, RH + DS-Cav1 1164 307_11mut- K196C-E60C-DS-Cav1_THS GSJnh1 Truncated D3 46-310 GG linker 1165 GSJnh2Truncated D3 46-310 GG linker 1166 GSJnh3 Truncated D3 51-305 GG linker1167 GSJnh4 Truncated D3 51-305 GSG linker 1168Domain III with trimer (22) RSVF ( + ) THS_ CP-D3 + DS-Cav1 + Fd146-306- Glycine linkers and Fd 1169 s_to_foldon ggsgg (Seq_1448)-50-105- ggsggsg (Seq_1445)- Fd RSVF ( + ) THS_ CP-D3 + RH + DS-Cav1 + 146-306- Glycine linkers and Fd 1170 s_to_hp2_ C-terminal Fdggsgg (Seq_1448)- foldon 50-105- ggsggsg (Seq_1445)- Fd RSVF ( + ) THS_CP-D3 + RH + DS-Cav1 +  146-306- Glycine linkers and Fd 1171 s_to_hp12_C-terminal Fd ggsgg (Seq_1448)- foldon 50-105- ggsggsg (Seq_1445)- FdRSVF ( + ) THS_ CP-D3 + RH + DS-Cav1 +  146-306- Glycine linkers and Fd1172 s_to_hp2_ C-terminal Fd ggsgg (Seq_1448)- foldon_I221F 50-105-ggsggsg (Seq_1445)- Fd RSVF ( + ) THS_ CP-D3 + RH + DS-Cav1 +  146-306-Glycine linkers and Fd 1173 s_to_hp2_ C-terminal Fd ggsgg (Seq_1448)-foldon_ds 50-105- ggsggsg (Seq_1445)- Fd RSVF ( + ) THS_CP-D3 + DS-Cav1 + Fd 146-306- Glycine linkers and Fd 1174 s_to_foldonggsgg (Seq_1448)- A102C-A241C 50-105- ggsggsg (Seq_1445)- FdRSVF ( + ) THS_ CP-D3 + RH + DS-Cav1 +  146-306- Glycine linkers and Fd1175 s_to_hp2_ C-terminal Fd ggsgg (Seq_1448)- foldon 50-105-A102C-A241C ggsggsg (Seq_1445)- Fd RSVF ( + ) THS_CP-D3 + RH + DS-Cav1 +  146-306- Glycine linkers and Fd 1176 s_to_hp12_C-terminal Fd ggsgg (Seq_1448)- foldon A102C- 50-105- A241C ggsggsg(Seq_1445)- Fd RSVF ( + ) THS_ CP-D3 + RH + DS-Cav1 +  146-306-Glycine linkers and Fd 1177 s_to_hp2_ C-terminal Fd ggsgg (Seq_1448)-foldon_I221F 50-105- A102C-A241C ggsggsg (Seq_1445)- Fd RSVF ( + ) THS_CP-D3 + RH + DS-Cav1 +  146-306- Glycine linkers and Fd 1178 s_to_hp2_C-terminal Fd ggsgg (Seq_1448)- foldon_ds 50-105- A102C-A241C ggsggsg(Seq_1445)- Fd GSJnhFd1 Truncated D3 + Fd Fd 1179 GSJnhFd2Truncated D3 + Fd Fd 1180 MS_01 D3 + C-terminal CCMPTD 51-103, 146-GGPGG (Seq_1451) linker 1181 307 turn, C-terminal CCMPTD MS_02D3 + C-terminal CCMPTD 51-103, 146- GGPGG (Seq_1451) turn, 1182 307longer linker, C- terminal CCMPTD MS_03 D3 + N-terminal CCMPTD51-103, 139- GGPGG (Seq_1451) turn, C- 1183 307 terminal CCMPTD MS_04D3 + N-terminal CCMPTD 51-103, 137- GGPGG (Seq_1451) turn 1184 307plus fusion peptide, C- terminal CCMPTD MS_05 D3 + N-terminal CCMPTD51-103, 146- GGPGG (Seq_1451) turn, C- 1185 307 terminal CCMPTD MS_06CP-D3, C-terminal MTQ- 51-103, 146- GGPGG (Seq_1451) turn, C- 1186 CC307 terminal MTQ-CC MS_07 CP-D3, C-terminal MTQ- 51-103, 146-GGPGG (Seq_1451) turn, 1187 CC 307 longer linker, C- terminal MTQ-CCMS_08 CP-D3, N-terminal MTQ- 51-103, 146- GGPGG (Seq_1451) turn, C- 1188CC |307 terminal MTQ-CC MS_09 CP-D3, N-terminal MTQ- 51-103, 139-GGPGG (Seq_1451) turn 1189 CC 307 plus fusion peptide, C-terminal MTQ-CC MS_10 CP-D3, N-terminal MTQ- 51-103, 139-GGPGG (Seq_1451) turn 1190 CC 307 plus fusion peptide, C-terminal MTQ-CC Tandem domain III (18) GSJnh1-TWIN TD3 (47-307,Glycine linkers 1191 103GG147) GSG (47-307, 103GG147) GSJnh2-TWIN TD3(47-307, Glycine linkers 1192 104GSG146) GSG 4(7-307, 104GSG146)GSJnh3-TWIN TD3 (51-305, Glycine linkers 1193 103GG147) GSG 1(5-305,103GG147) GSJnh4-TWIN TD3 (51-305, Glycine linkers 1194 104GSG146) GSG(51-305, 104GSG146) GSJnh1- TD3 (47-307, Glycine linkers 1195 TWINLg103GG147) GGGSG GGG (47-307, 103GG147) GSJnh2- TD3 (47-307,Glycine linkers 1196 TWINLg 104GSG146) GGGS GGGG (47-307, 104GSG146)GSJnh3- TD3 (51-305, Glycine linkers 1197 TWINLg 103GG147) GGGSGGGG (51-305, 103GG147) GSJnh4- TD3 (51-305, Glycine linkers 1198 TWINLg104GSG146) GGGS GGGG (51-305, 104GSG146) LC-DH01 CP-TD3 + long linker145-306, 52-96 GGGSGGGSGGGSGGG (Seq_1452) 1199 linker LC-DH02CP-TD3 + long linker +  145-306, 52-96 GGGSGGGSGGGSGGG (Seq_1452) 1200DS linker LC-DH03 CP-TD3 + short linker 145-306, 52-96 GGGSGGGSGGG 1201(Seq_1453) linker LC-DH04 CP-TD3 + short linker 145-306, 52-96GGGSGGGSGGG (Seq_1453) 1202 linker LC-DH05 LM leader + CP-TD3 + 145-306, 52-96 GGGSGGGSGGG (Seq_1453) 1203 short linker linker LC-DH06LM leader + CP-TD3 +  145-306, 52-96 GGGSGGGSGGG 1204 short linker + DS(Seq_1453) linker LC-DH07 LM leader + CP-TD3 +  145-306, 52-96GGGSGGGSGGGSGGG 1205 long linker (Seq_1452) linker LC-DH08LM leader + CP-TD3 +  145-306, 52-96 GGGSGGGSGGGSGGG (Seq_1452) 1206long linker + DS linker LC-DH09 LM leader + CP-TD3 +  145-306, 52-96GGGSGGGSGGG (Seq_1453) 1207 long linker + Arg linker LC-DH10LM leader + CP-TD3 +  145-306, 52-96 GGGSGGGSGGG (Seq_1453) 1208long linker + Arg + DS linker  Tandem domain III with a trimer (10)GSJnh1Fd- TD3 + Fd (47-307, Glycine linkers 1209 TWIN 103GG147) GG-Fd-GG (47-307,  103GG147) GSJnh2Fd- TD3 + Fd (47-307, Glycine linkers1210 TWIN 104GSG146) GG- Fd-GG (47-307, 104GSG146) GSJnh3Fd- TD3 + Fd(51-305, Glycine linkers 1211 TWIN 103GG147) GG- Fd-GG (51-305,103GG147) GSJnh4Fd- TD3 + Fd (51-305, Glycine linkers 1212 TWIN104GSG146) GG- Fd-GG (51-305, 104GSG146) GSJnhFd3a TD3 + Fd(F1/GSG/F2/Fd/ Glycine linkers 1213 TWIN F1/GSG/F2/Thbn/ H/S) GSJnhFd3bTD3 + Fd (H/S/Thbn/F1/GSG/ Glycine linkers 1214 TWIN F2/Fd/F1/GSG/F2)GSJnh1- TD3 + Fd (47-307, Glycine linkers 1215 TWINGFd 103Fd147) GSGGSG(47-307, 103GG147) GSJnh2- TD3 + Fd (47-307, Glycine linkers 1216TWINGFd 104Fd146) GSGGSG  (47-307, 104GSG146) GSJnh1- TD3 + Fd (47-307,Glycine linkers 1217 TWINFdG 103Fd147) GSGGSG (47-307, 103GG147) GSJnh2-TD3 + Fd (47-307, Glycine linkers 1218 TWINFdG 104Fd146) GSGGSG (47-307,104GSG146)

TABLE 21 Minimal site Ø immunogens on a protein nanoparticle.scaffold or SEQ Construct RSV F Region other added His tag ID nameConcept Particle (residue #s) protein (N, I or C) NODomain III on ferritin (45) GSJnh1F TD3 + Fer Fer 46-103 GG 147-GGlinker, C- N-H8- 1219 310 terminal Fer Strep-GG- Thr-GGS GSJnh2FTD3 + Fer Fer 46-104 GSG GSG linker, N-H8- 1220 146-310 C-term. FerStrep-GG- Thr-GGS GSJnh3F TD3 + Fer Fer 51-103 GG 147-GG linker, C-N-H8- 1221 305 term. Fer Strep-GG- Thr-GGS GSJnh4F TD3 + Fer Fer51-104 GSG GSG linker, N-H8- 1222 146-305 C-term. Fer Strep-GG- Thr-GGSTK_01 CP-SØ + DS + DPS Dps 59-97, 194-240 Dps N-H6-Thr 1223 TK_02CP-SØ + DS + DPS Dps 59-97, 194-240 Dps N-H6-Thr 1224 TK_03CP-SØ + DS + DPS Dps 59-97, 194-240 Dps N-H6-Thr 1225 TK_04CP-SØ + DS + DPS Dps 59-97, 194-240 Dps N-H6-Thr 1226 TK_05CP-SØ + CAV + 59-97, 194-240 Dps N-H6-Thr 1227 DPSDps TK_06CP-SØ + CAV + 59-97, 194-240 Dps N-H6-Thr 1228 DPSDps TK_07CP-SØ + CAV + 59-97, 194-240 Dps N-H6-Thr 1229 DPSDps TK_08CP-SØ + CAV + 59-97, 194-240 Dps N-H6-Thr 1230 DPSDps TK_09 CP- Dps59-97, 194-240 Dps N-H6-Thr 1231 SØ + CAV + DS + DPS TK_10 CP- Dps59-97, 194-240 Dps N-H6-Thr 1232 SØ + CAV + DS + DPS TK_11 CP- Dps59-97, 194-240 Dps N-H6-Thr 1233 SØ + CAV + DS + DPS TK_12 CP- Dps59-97, 194-240 Dps N-H6-Thr 1234 SØ + CAV + DS + DPS TK_13D3 + DS + CAV + Fer 53-97, 148-305 Fer N-H6-Thr 1235 Fer TK_14D3 + DS + CAV + Fer 53-97, 148-306 Fer N-H6-Thr 1236 Fer TK_15D3 + DS + CAV + Fer 53-97, 148-307 Fer N-H6-Thr 1237 Fer TK_16D3 + DS + CAV + Fer 53-97,148-308 Fer N-H6-Thr 1238 Fer TK_17D3 + DS + CAV + Fer 53-97, 148-309 Fer N-H6-Thr 1239 Fer TK_18D3 + DS + CAV + Fer 53-97, 148-310 Fer N-H6-Thr 1240 Fer TK_19D3 + DS + CAV + Fer 53-97, 148-311 Fer N-H6-Thr 1241 Fer TK_20D3 + DS + CAV + Fer 53-97, 148-312 Fer N-H6-Thr 1242 Fer TK_21D3 + DS + CAV + Fer 53-97, 148-313 Fer N-H6-Thr 1243 Fer TK_22D3 + DS + CAV + Fer 53-97, 148-314 Fer N-H6-Thr 1244 Fer TK_23D3 + DS + CAV + Fer 53-97, 148-315 Fer N-H6-Thr 1245 Fer TK_24D3 + DS + CAV + Fer 53-97, 148-316 Fer N-H6-Thr 1246 Fer TK_25D3 + DS + CAV + Fer 53-97, 148-317 Fer N-H6-Thr 1247 Fer TK_26D3 + DS + CAV + Fer 53-97, 148-318 Fer N-H6-Thr 1248 Fer TK_27D3 + DS + CAV + Fer 53-97, 148-319 Fer N-H6-Thr 1249 Fer TK_28D3 + DS + CAV + Fer 53-97, 148-320 Fer N-H6-Thr 1250 Fer TK_29D3 + DS + RH + Fer 53-104, 145-307 Fer N-H6-Thr 1251 Fer TK_30D3 + DS + RH + Fer 53-104, 145-307 Fer N-H6-Thr 1252 Fer RSVF (+) CP-D3, RH +  Fer 146-306- Glycine N-Strep- 1253 THS_s_to + DS-Cav1 + Fer ggsgg (Seq_1448)- linkers, Fer H8-HRV3C Fer_31n 50-105-sgg-Fer RSVF (+) CP-D3, RH +  Fer 146-306- Glycine N-Strep- 1254THS_s_to_  DS-Cav1 + Fer ggsgg (Seq_1448)- linkers, Fer H8-HRV3C hp2 +50-105- Fer_31n sgg-Fer RSVF (+) CP-D3, RH +  Fer 146-306- GlycineN-Strep- 1255 THS_s_to +  DS-Cav1 + Fer ggsgg (Seq_1448)- linkers, FerH8-HRV3C Fer_51n 50-105- ggsgg  (Seq_1448)-Fer RSVF (+) CP-D3, RH +  Fer146-306- Glycine N-Strep- 1256 THS_s_to_  DS-Cav1 + Ferggsgg (Seq_1448)- linkers, Fer H8-HRV3C hp2 + 50-105- Fer_51nggsgg (Seq_1448)- Fer RSVF (+)  CP-D3, RH +  Fer 146-306- GlycineN-Strep- 1257 THS_s_to_ DS-Cav1 + Fer ggsgg (Seq_1448)- linkers, FerH8-HRV3C hp12 + 50-105- Fer_51n ggsgg (Seq_1448)- Fer RSVF (+)CP-D3, RH +  Fer 146-306- Glycine N-Strep- 1258 THS_s_to_  DS-Cav1 + Ferggsgg (Seq_1448)- linkers, Fer H8-HRV3C hp2 + 50-105- Fer_31n_I221Fsgg-Fer RSVF (+)   CP-D3, RH +  Fer 146-306- Glycine N-Strep- 1259THS_s_to_ DS-Cav1 + Fer ggsgg (Seq_1448)- linkers, Fer H8-HRV3Chp2 + Fer_ 50-105- 51n_I221F ggsgg (Seq_1448)- Fer MP1 D3 + Cav + FerFer 50-306 GSG Glycine N-Strep- 1260 linker, Fer H8-Thr MP2D3 + Cav + Fer Fer 50-306 Glycine N-Strep- 1261 GGSGG (Seq_1448)linker, Fer H8-Thr MP10 D3 + Fer Fer SC- Glycine N-Strep- 1262GGSGG (Seq_1448) linker, Fer H8-Thr MP11 D3 + Fer Fer SC- GlycineN-Strep- 1263 GGSGG (Seq_1448) linker, Fer H8-ThrMinimal epitope with trimer on ferritin (1) MP 9 Minimal CP- Fer56-76 G- Fer N-Strep- 1264 SØ + ATCase ATCase-G- H8-Thr trimerization189- domain + Fer 211GGSGG (Seq_1448)Domain III with trimer on ferritin (4) GSJnh1Fd-F Truncated sc Fer46-310 103GG147, C- IN- 1265 D3 + Fd + Fer term. Fd-Fer H8 StrepGG-Thr-GGS GSJnh2Fd-F Truncated sc Fer 46-310 104GSG146, N- 1266D3 + Fd + Fer C-term. Fd- H8 StrepGG- Fer Thr-GGS GSJnh3Fd-FTruncated sc Fer 51-305 103GG147, C- C-term. 1267 D3 + Fd + Ferterm. Fd-Fer H8StrepGG- Thr-GGS GSJnh4Fd-F Truncated sc Fer 51-305104GSG146, C-term. 1268 D3 + Fd + Fer c-term. Fd- H8 StrepGG- FerThr-GGS Minimal epitope on ferritin (10) JCB_22 CP-SØ + Fer Fer60-94, 192- PGG linker, N-H6-HRV3C 1269 229 Fer JCB_23 CP-SØ + Fer Fer60-94, 192- PGG linker, N-H6-HRV3C 1270 229 Fer JCB_24 CP-SØ + Fer Fer60-94, 192- PGG linker, N-H6-HRV3C 1271 229 Fer JCB_25 CP-SØ + Fer Fer60-94, 192- GSG linker, N-H6-HRV3C 1272 229 Fer JCB_26 CP-SØ + Fer Fer60-94, 192- GSG linker, N-H6-HRV3C 1273 229 Fer JCB_27 CP-SØ + Fer Fer60-94, 192- GSG linker, N-H6-HRV3C 1274 229 Fer 2m0e-resurf1-Minimal SØ on Fer Miz-1 zinc N-Strep, 1275 Fer a 2MOE + Fer finger 6H6, Thr (2M0E) fragment + Fer 2m0e-resurf1- Minimal SØ on Fer Miz-1 zincN-Strep, 1276 Fer a 2MOE + Fer finger 6 H6, Thr (2M0E) fragment + FerMP3 CP-SØ + Fer Fer 56-97 GG GG N-Strep-H8- 1277 189-240 GSGlinker + Fer Thr MP4 CP-SØ + Fer Fer same as MP3 GGSGG N-Strep-H8- 1278with (Seq_1448) Thr GGSGG (Seq_1448) linker + FerMinimal epitope on LS (2) 2m0e-resurf1- Minimal SØ on a LS LSC-term. Thr 1279 LS 2MOE + LS H6-strep 2m0e-resurf1- Minimal SØ on HCP1HCP1 C-term. Thr 1280 1y12 a 2M0E + hcp1 H6-strep Domain III on LS (2)LS1-E- CP-D3, RH +  LS LS N-Strep, 1281 CP_RBD51- DS-Cav1 + LS H6, Thr307_11mutDS- Cav1_THS LS2-E- CP-D3, RH +  LS LS N-Strep, 1282 CP_RBD51-H6, Thr 307_11mutDS- DS-Cav1 + LS Cav1_THS Domain III on hcp1 (4)1y12-E- CP-D3, RH +  HCP1 HCP1 C-term. Thr 1283 CP_RBD51- DS-Cav1 + hcp1H6-strep 307_11mutDS- Cav1_THS 1y12-E- CP-D3, RH +  HCP1 HCP1C-term. Thr 1284 RBD51- DS-Cav1 + hcp1 H6-strep 307_11mut_ DS-Cav1_THS1y12-E- CP-D3, RH +  HCP1 HCP1 C-term. Thr 1285 CP_RBD51- DS-Cav1 + hcp1H6-strep 307_14mutDS- Cav1_THS ly12-E-RBD51- CP-D3, RH +  HCP1 HCP1C-term. Thr 1286 307_14mut_DS- DS-Cav1 + hcp1 H6-strep Cav1_THS JCB_1_CP-SØ + CAV + 60-94, 192- APGG N-Strep-H8- 1287 GSGGSG_ferr FerFer 232linker + Fer Thr JCB_2_ CP-SØ + CAV + 60-94, 192- APGG linker,N-Strep-H8- 1288 GSGGSG_ferr FerFer 232 DS + Fer Thr JCB_5_CP-SØ + CAV + 60-94, 192- AGSG linker, N-Strep-H8- 1289 GSGGSG_ferrFerFer 232 DS + Fer Thr JCB_7_ CP-SØ + CAV + 60-94, 192- GSG N-Strep-H8-1290 GSGGSG_ferr FerFer 229 linker + Fer Thr JCB_8_ CP-SØ + CAV +60-94, 192- GSG linker, N-Strep-H8- 1291 GSGGSG_ferr FerFer 229 DS + FerThr JCB_28_ D3 + CAV + Fer Fer 53-96, 149- Glycine N-Strep-H8- 1292GSGGGSG_ferr 304 linkers, Fer Thr TZ_09r_GGSG_ CP- Fer 192-242, 60-Glycine N-Strep-H8- 1293 ferr SØ + DS + CAV + 97 linkers, Fer Thrglycan + Fer TZ_12r_GGSG_ CP- Fer 192-242, 60- Glycine N-Strep-H8- 1294Ferr SØ + DS + CAV + 97 linkers, Fer Thr charge + Fer TZ_13r_GGSG_ CP-Fer 192-242, 60- Glycine N-Strep-H8- 1295 Ferr SØ + DS + CAV + 97linkers, Fer Thr glycan + Fer TZ_14r_GGG_ CP- Fer 192-242, 60- GlycineN-Strep-H8- 1296 Ferr SØ + DS + CAV + 97 linkers, Fer Thr cglyan + FerSite_0_1chd_ CP- Fer 60-95, 192- CheB N-Strep-H8- 1297 3_GYC_GGSØ + CAV + RH + 240 methylesterase Thr SGGSGGSGGSGGG_ DS +  fragmentferr section of 1CHD (1CHD) + Fer scaffold + Fer JG_circl_sol_CP-SØ + DS + Fer Fer 60-94, 193- Glycine N-Strep-H8- 1298 ds_ferr 237linkers, Fer Thr JG_2KN0_ferr CP-SØ + section Fer 60-75, 193- GlycineN-Strep-H8- 1299 of TENC1 (2KNO) 218 linkers + TENC Thr scaffold + Fer1 (2KNO) scaffold + Fer JG_Circ2_ferr CP-SØ + Fer Fer 60-75, 193-Glycine N-Strep-H8- 1300 218 linkers, Fer Thr JG_Circ2_sol _ CP-SØ + FerFer 60-75, 193- Glycine N-Strep-H8- 1301 Ferr 218 linkers, Fer ThrGSJnh2-Fer Truncated sc Fer 46-310 Glycine N-H8- 1302 D3 linkers, FerStrep-Thr GSJnh3-Fer Truncated sc Fer 51-305 Glycine N-H8- 1303 D3linkers, Fer Strep-Thr GSJnh4-Fer Truncated sc Fer 51-305 Glycine N-H8-1304 D3 linkers, Fer Strep-Thr GSJnh2-TWIN- TD3 Fer 47-307, 47- GlycineN-H8- 1305 Fer 307 linkers, Fer Strep-Thr GSJnh3-TWIN- TD3 Fer51-305, 51- Glycine N-H8- 1306 Fer 305 linkers, Fer Strep-ThrGSJnh4-TWIN- TD3 Fer 51-305, 51- Glycine N-H8- 1307 Fer 305 linkers, FerStrep-Thr GSJnh2Fd-TWIN- TD3 with Fd Fer 47-307, 47- Glycine N-H8- 1308Fer 307 linkers + T4 Strep-Thr Fd + Fer GSJnh4Fd-TWIN- TD3 with Fd Fer51-305, 51- Glycine N-H8- 1309 Fer 305 linkers + T4 Strep-Thr Fd + FerGSJnhFd2-Fer TD3 with Fd Fer Glycine N-H8- 1310 linkers + T4 Strep-ThrFd + Fer GSJnh2-TWINLg- TD3 Fer 47-307, 47- Glycine N-H8- 1311 Fer 307linkers, Fer Strep-Thr GSJnh3-TWINLg- TD3 Fer 51-305, 51- Glycine N-H8-1312 Fer 305 linkers, Fer Strep-Thr GSJnh4-TWINLg- TD3 Fer 51-305, 51-Glycine N-H8- 1313 Fer 305 linkers, Fer Strep-Thr RSVF (+)  CP D3 + DS-Fer 146-306- Glycine N-Strep-H8- 1314 THS_s_to Cav1 ggsgg (Seq_1448)-linkers, Fer HRV3C A102C-A241C_ 50-105 sgg_ferr RSVF (+) CP D3 + DS- Fer146-306- Glycine HRV3C 1315 THS_s_to_ Cav1 + Fd ggsgg (Seq_1448)-linkers, Fer N-Strep-H8- foldon A102C- 50-105- A241C_ ggsggsgggsggggsgg_ferr (Seq_1445)- Fd RSVF (+) CP D3 + EH +  Fer 146-306-Glycine HRV3C 1316 THS_s_to_hp12 DS-Cav1 ggsgg (Seq_1448)- linkers, FerN-Strep-H8- A102C-A241C_ 50-105 ggsgg_ferr RSVF (+) CP D3 + EH +  Fer146-306- Glycine N-Strep-H8- 1317 THS_s_to_hp123  DS-Cav1ggsgg (Seq_1448)- linkers, Fer HRV3C A102C-A241C_ 50-105 ggsgg_ferrRSVF (+) CP D3 + EH +  Fer 146-306- Glycine HRV3C 1318 THS_s_to_hp1234 DS-Cav1 ggsgg (Seq_1448)- linkers, Fer N-Strep-H8- A102C-A241C_ 50-105ggsgg_ferr RSVF (+) CP D3 + EH +  Fer 146-306- Glycine N-Strep-H8- 1319THS_s_to_hp123_ DS-Cav1 ggsgg (Seq_1448)- linkers, Fer HRV3C ggsgg_ferr50-105 RSVF (+) CP D3 + EH +  Fer 146-306- Glycine N-Strep-H8- 1320THS_s_to_hp2 DS-Cav1 ggsgg (Seq_1448)- linkers, Fer HRV3C A102C-A241C_50-105 sgg_ferr RSVF (+) CP D3 + EH +  Fer 146-306- Glycine HRV3C 1321THS_s_to_hp23 DS-Cav1 ggsgg (Seq_1448)- linkers, Fer N-Strep-H8-A102C-A241C_ 50-105 sgg_ferr RSVF (+) THS_ CP D3 + EH +  Fer 146-306-Glycine HRV3C 1322 to hp23_ DS-Cav1 ggsgg  Seq_1448)- linkers, FerN-Strep-H8- ggsgg_ferr 50-105 RSVF (+)  CP D3 + EH +  Fer 146-306-Glycine HRV3C 1323 THS_s_to_hp2_  DS-Cav1 ggsgg (Seq_1448)- linkers, FerN-Strep-H8- ds A102C- 50-105 A241C_sgg_ferr RSVF (+) CP D3 + EH +  Fer146-306- Glycine HRV3C 1324 THS_s_to_hp2_ DS-Cav1 ggsgg-50- linkers, FerN-Strep-H8- ds_ggsgg_ferr 105 RSVF (+)  CP D3 + EH +  Fer 146-306-Glycine HRV3C 1325 THS_s_to_hp2_ DS-Cav1 ggsgg (Seq_1448)- linkers, FerN-Strep-H8- I221F A102C- 50-105 A241C_sgg_ferr C-Trimer Fer: CP-SØ + FerFer Glycine N-Leader- 1326 leader-Strep- linker + Fer Strep- HISx6-Thr-HISx6-Thr L1H1-K1-H2L2H3- GGSG  Monomers on LS (44) JCB_1_GSGGSG_CP-SØ + CAV + LS LS 60-94, 192- APGG c-term. 1327 LS 232 linker + LSThr, Strep, and H8 JCB_2_GSGGSG_ CP-SØ + CAV + LS ILS 60-94, 192-APGG linker, C-term. 1328 LS 232 DS + LS Thr, Strep, and H8JCB_5_GSGGSG_ CP-SØ + CAV + LS LS 60-94, 192- AGSG linker, C-term. 1329LS 232 DS + LS Thr, Strep, and H8 JCB_7_GSGGSG_ CP-SØ + CAV + LS LS60-94, 192- GSG linker + Thr, Strep, 1330 LS 229 LS C-term. and H8JCB_8_GSGGSG_ CP-SØ + CAV + LS LS 60-94, 192- GSG linker, C-term. 1331LS 229 DS + LS Thr, Strep, and H8 JCB_28_GSGGSG_ D3 + CAV + LS LS53-96, 149- Glycine C-term. 1332 LS 304 linkers + LS Thr, Strep, and H8TZ_12r_GGSGG_ CP- LS 192-242, 60- Glycine N-Strep-H8- 1333 LSSØ + DS + CAV + 97 linkers + LS Thr charge + LS TZ_13r_GGSGG_ CP- LS192-242, 60- Glycine N-Strep-H8- 1334 LS SØ + DS + CAV + 97 linkers + LSThr glycan + LS TZ_14r_GGSGSG_ CP- LS 192-242, 60- Glycine N-Strep-H8-1335 LS SØ + DS + CAV + 97 linkers + LS Thr glycan + LS Site_0_1chd_ CP-LS 60-95, 192- CheB c-term. 1336 3_GYC_GGSG SØ + CAV + RH + 240methylesterase Thr-H6Strep GSGGSGGSGGG_ DS + section of fragment LS 1CHD(1CHD) + LS scaffold + LS JG_circl_sol_ CP-SØ + DS + LS LS 60-94, 193-Glycine C-Thr-His- 1337 ds_LS 237 linkers + LS Strep JG_2KN0_LSCP-SØ + section LS 60-75, 193- Glycine C-Thr-His- 1338 of TENC1 218linkers + TENC1 Strep (2KNO) (2KNO) scaffold + LS scaffold + FerJG_Circ2_LS CP-SØ + LS LS 60-75, 193- Glycine C-Thr-His- 1339 218linkers + LS Strep JG_Circ2_sol_ CP-SØ + LS LS 60-75, 193- GlycineC-Thr-His- 1340 LS 218 linkers + LS Strep GSJnh2-LS Truncated sc LS46-310 Glycine N-H8- 1341 D3 linkers, LS Strep-Thr GSJnh3-LSTruncated sc LS 51-305 Glycine N-H8- 1342 D3 linkers, LS Strep-ThrGSJnh4-LS Truncated sc LS 51-305 Glycine N-H8- 1343 D3 linkers, LSStrep-Thr GSJnh2-TWIN-LS TD3 LS 47-307, 47- Glycine N-H8- 1344 307linkers, LS Strep-Thr GSJnh3-TWIN-LS TD3 LS 51-305, 51- Glycine N-H8-1345 305 linkers, LS Strep-Thr GSJnh4-TWIN-LS TD3 LS 51-305, 51- GlycineN-H8- 1346 305 linkers, LS Strep-Thr GSJnh2Fd-TWIN- TD3 with Fd LS47-307, 47- Glycine N-H8- 1347 LS 307 linkers + T4 Strep-Thr Fd + LSGSJnh4Fd-TWIN- TD3 with Fd LS 51-305, 51- Glycine N-H8- 1348 LS 305linkers + T4 Strep-Thr Fd + LS GSJnhFd2-LS TD3 with Fd LS Glycine N-H8-1349 linkers + T4 Strep-Thr Fd + LS GSJnh2-TWINLg- TD3 LS 47-307, 47-Glycine N-H8- 1350 LS 307 linkers, LS Strep-Thr GSJnh3-TWINLg- TD3 LS51-305, 51- Glycine N-H8- 1351 LS 305 linkers, LS Strep-ThrGSJnh4-TWINLg- TD3 LS 51-305, 51- Glycine N-H8- 1352 LS 305 linkers, LSStrep-Thr RSVF (+)  CP D3 + DS- LS 146-306- Glycine N-Strep-H8- 1353THS_s_to_gagg Cav1 ggsgg (Seq_1448)- linkers, LS HRV3C gsggsggsggg_ls50-105 RSVF (+) CP D3 + EH +  LS 146-306- Glycine N-Strep-H8- 1354THS_s_to_hp2_ DS-Cav1 ggsgg (Seq_1448)- linkers, LS HRV3C gagggsggsggsg50-105 gg_ls RSVF (+) CP D3 + EH +  LS 146-306- Glycine N-Strep-H8- 1355THS_s_to_hp12_ DS-Cav1 ggsgg (Seq_1448)- linkers, LS HRV3C gagggsggsggs50-105 ggg_ls RSVF (+) CP D3 + EH +  LS 146-306- Glycine N-Strep-H8-1356 THS_s_to_hp2 DS-Cav1 ggsgg (Seq_1448)- linkers, LS HRV3CI221F_gagggsggs 50-105 ggsggg_ls RSVF (+) CP D3 + DS- LS 146-306-Glycine N-Strep-H8- 1357 THS_s_to Cav1 ggsgg (Seq_1448)- linkers, LSHRV3C A102C- 50-105 A241C_gag ggsggsggsggg_ls RSVF (+) CP D3 + DS- LS146-306- Glycine N-Strep-H8- 1358 THS_s_to_hp12 Cav1 + Fdggsgg (Seq_1448)- linkers + T4 HRV3C A102C- 50-105- Fd + LSA241C_gagggsg ggsggsg gsggsggg_ls (Seq_1445)- Fd RSVF (+) CP D3 + DS- LS146-306- Glycine N-Strep-H8- 1359 THS_s_to_hp123_ Cav1 + Fdggsgg (Seq_1448)- linkers + T4 HRV3C gagggsggsggs 50-105- Fd + LS ggg_lsggsggsg (Seq_1445)- Fd RSVF (+) CP D3 + EH +  LS 146-306- GlycineN-Strep-H8- 1360 THS_s_to_hp123 DS-Cav1 ggsgg (Seq_1448)- linkers, LSHRV3C A102C-A241C_gag 50-105 ggsggsggsggg_ls RSVF (+) THS_ CP D3 + EH + LS 146-306 Glycine N-Strep-H8- 1361 s_to_hp1234 DS-Cav1ggsgg (Seq_1448)- linkers, LS HRV3C A102C-A241C_gag 50-105ggsggsggsggg_ls RSVF (+) CP D3 + EH +  LS 146-306- Glycine N-Strep-H8-1362 THS_s_to_hp2 DS-Cav1 ggsgg (Seq_1448)- linkers, LS HRV3CA102C-A241C_gag 50-105 ggsggsggsggg_ls RSVF (+)  CP D3 + EH +  LS146-306- Glycine N-Strep-H8- 1363 THS_s_to_hp2 DS-Cav1 ggsgg (Seq_1448)-linkers, LS HRV3C ds_gagg 50-105 gsggsggsggg_ls RSVF (+) CP D3 + EH + LS 146-306- Glycine N-Strep-H8- 1364 THS_s_to_hp2 DS-Cav1 + Fdggsgg (Seq_1448)- linkers + T4 HRV3C ds A102C- 50-105- Fd + LSA241C_gagg ggsggsg gsggsggsggg_ls (Seq_1445)- Fd RSVF (+) CP D3 + EH + LS 146-306- Glycine N-Strep-H8- 1365 THS_s_to_hp2 DS-Cav1 + Fdggsgg (Seq_1448)- linkers + T4 HRV3C I221F A102C- 50-105- Fd + LSA241C_gagggs ggsggsg ggsggsggg_ls (Seq_1445)- Fd RSVF (+) CP D3 + EH + LS 146-306- Glycine N-Strep-H8- 1366 THS_s_to_hp23_ DS-Cav1ggsgg (Seq_1448)- linkers, LS HRV3C gagggsggsggsg 50-105 gg_ls RSVF (+)CP D3 + EH +  LS 146-306- Glycine N-Strep-H8- 1367 THS_s_to_hp23 DS-Cav1ggsgg (Seq_1448)- linkers, LS HRV3C A102C-A241C_gag 50-105ggsggsggsggg_ls C-Trimer LS: CP-SØ + LS LS Glycine N- Leader- 1368leader-Strep- linker + LS Strep- HISx6-Thr- HISx6-Thr L1H1-K1-H2L2H3-GGSGGGSG C-Trimer LS: CP-SØ + LS LS Glycine C-Leader- 1369 leader-L1H1-linker + LS Thr-H6- K1-H2L2H3- Strep GGSGGGSG-LS- Thr- HISx6-Strep:Trimers on ferritin (30) JCB_13_ CP- Fer 60-94, 192- APGG linker,N-Strep-H8- 1370 GSGGGSG_ferr SØ + CAV + DS + 232 GCN4, inter- ThrGCN4 + Fer DS + Fer JCB_19_ CP- Fer 60-94, 192- GSG linker, N-Strep-H8-1371 GSGGSG_ferr SØ + CAV + DS + 229 GCN4, inter- Thr GCN4 + FerDS + Fer TZ_05_GGSG_ CP- Fer 192-242, 60- Glycine N-Strep-H8- 1372 ferrsØ + interchain 97 linkers, Fer Thr DS + CAV + charge + Fer TZ_08r_GGSG_CP- Fer 192-242, 60- Glycine N-Strep-H8- 1373 ferr sØ + interchain 97linkers, Fer Thr DS + CAV + glycan + Fer TZ_15_GGSG_ CP- Fer 58-97, 192-Glycine N-Strep-H8- 1374 3Hferr SØ + interchain 242 linkers + ThrDS + CXVIII + Fer CXVIII + Fer TZ_16_GGSG_ CP- Fer 58-97, 192- GlycineN-Strep-H8- 1375 3Hferr SØ + interchain 242 linkers + ThrDS + CAV + CXVIII CXVIII + Fer + Fer TZ_17_GGSGSG_ CP- Fer 58-97, 192-Glycine N-Strep-H8- 1376 3Hferr SØ + interchain 242 linkers + ThrDS + CAV + CXVIII CXVIII + Fer + Fer TZ_19_GGSGSGG_ CP- Fer 58-97, 192-Glycine N-Strep-H8- 1377 3Hferr SØ + interchain 242 linkers + ThrDS + CAV + charge CXVIII + Fer + glycan + CXVIII + Fer TZ_19_GGSGG_ CP-Fer 58-97, 192- Glycine N-Strep-H8- 1378 ferr sØ + interchain 242linkers, Fer Thr DS + CAV + charge + glycan + Fer TZ_20_GGSGSGG_ CP- Fer58-97, 192- Glycine N-Strep-H8- 1379 3Hferr SØ + DS + CAV + 242linkers + Thr charge + CXVIII + Fer glycan + CXVIII + Fer MS_03_D3 + N-term. Fer 51-103, 139- Glycine N-Strep-H8- 1380 GGGSSGSGGGSSGGCCMPTD + Fer 307 linkers, Fer Thr GSSGGGS_Ferr MS_05_ D3 + N-term. Fer51-103, 146- Glycine N-Strep-H8- 1381 GGGSSGSGGGSSGG CCMPTD + Fer 307linkers, Fer Thr GSSGGGS_Ferr MS_07_ CP-D3, C- Fer 51-103, 146- GlycineN-Strep-H8- 1382 GSGGGSSGSGGG term. MTQ- 307 linkers, Fer ThrSSGGGSSGGGS_ CC + Fer Ferr MS_08 CP-D3, C- Fer 51-103, 146- GlycineN-Strep-H8- 1383 GGGSSGSGGGSS term. MTQ- 307 linkers, Fer Thr GGGSSGGGS_CC + Fer Ferr MS_09_GGGSSGS CP-D3, C- Fer 51-103, 139- GlycineN-Strep-H8- 1384 GGGSSGGGSSGGGS_ term. MTQ- 307 linkers, Fer Thr FerrCC + Fer GSJnh2-Fer A74C Truncated sc Fer 46-310 Glycine N-H8- 1385E218C D3, linkers, Fer Strep-Thr interchain DS GSJnh3-Fer A74CTruncated sc Fer 51-305 Glycine N-H8- 1386 E218C D3, linkers, FerStrep-Thr interchain DS GSJnh4-Fer A74C Truncated sc Fer 51-305 GlycineN-H8- 1387 E218C D3, linkers, Fer Strep-Thr interchain DS GSJnh4-TWIN-TD3, Fer 51-305, 51- Glycine N-H8- 1388 Fer A74C interchain DS 305linkers, Fer Strep-Thr E218C RSVF (+) CP D3 + DS- Fer 146-306- GlycineN-Strep-H8- 1389 THS_s_to_ Cav1 +  ggsgg (Seq_1448)- linkers, Fer HRV3Cfoldon_ Fd 50-105- ggsggggsgg_ferr ggsggsg (Seq_1445)- Fd RSVF (+)CP D3 + EH +  Fer 146-306- Glycine N-Strep-H8- 1390 THS_s_to_hp12DS-Cav1 + Fd ggsgg (Seq_1448)- linkers + T4 HRV3C foldon A102C- 50-105-Fd + Fer A241C_ ggsggsg ggsggggsgg_ferr (Seq_1445)- Fd RSVF ( + )CP D3 + EH +  Fer 146-306- Glycine N-Strep-H8- 1391 THS_s_to_hp12DS-Cav1 + Fd ggsgg (Seq_1448)- linkers + T4 HRV3C foldon_ 50-105-Fd + Fer ggsggggsgg_ferr ggsggsg (Seq_1445)- Fd RSVF (+) CP D3 + EH + Fer 146-306- Glycine N-Strep-H8- 1392 THS_s_to_hp2 DS-Cav1 + Fdggsgg (Seq_1448)- linkers + T4 HRV3C foldon A102C- 50-105- Fd + FerA241C_ ggsggsg ggsggggsgg_ferr (Seq_1445)- Fd RSVF (+) CP D3 + EH +  Fer146-30- Glycine N-Strep-H8- 1393 THS_s_to_hp2 DS-Cav1 ggsgg (Seq_1448)-linkers, Fer HRV3C foldon_ds 50-105 A102C-A241C_ ggsggggsgg_ferrRSVF (+) CP D3 + EH +  Fer 146-306- Glycine N-Strep-H8- 1394THS_s_to_hp2 DS-Cav1 + Fd ggsgg (Seq_1448)- linkers + T4 HRV3Cfoldon_ds_ 50-105- Fd + Fer ggsggggsggferr ggsggsg (Seq_1445) FdRSVF (+) CP D3 + EH +  Fer 146-306- Glycine N-Strep-H8- 1395THS_s_to_hp2_ DS-Cav1 + Fd ggsgg (Seq_1448)- linkers + T4 HRV3C foldon_50-105- Fd + Fer ggsggggsgg_ferr ggsggsg (Seq_1445)- Fd RSVF (+)CP D3 + EH +  Fer 146-306- Glycine N-Strep-H8- 1396 THS_s_to_hp2DS-Cav1 + Fd ggsgg (Seq_1448)- linkers + T4 HRV3C foldon_I221F  50-105-Fd + Fer A102C-A241C_ ggsggsg ggsggggsgg_ferr (Seq_1445)- Fd RSVF ( + )CP D3 + EH +  Fer 146-306- Glycine N-Strep-H8- 1397 THS_s_to_hp2DS-Cav1 + Fd ggsgg (Seq_1448)- linkers + T4 HRV3C foldon_I221F_ 50-105-Fd + Fer ggsggggsgg_ferr ggsggsg (Seq_1445)- Fd C-Trimer 1GQ3-CP-SØ + C-term. Fer Glycine N-Leader- 1398 Fer: leader- ATCase + Ferlinkers + Strep- Strep-HISx6- ATCase (1GQ3) HISx6-Thr Thr-L1H1-K1- + FerH2L2H3- GGSGGGSG-1GQ3- GGSGGGSGGGSG GGSG-Fer C-Trimer 1GQ3-CP-SØ + C-term. Fer Glycine  Strep- 1399 Fer: leader- ATCase + Ferlinkers + N-Leader- Strep-HISx6- ATCase (1GQ3) HISx6-Thr Thr-L1H1-K1-+ Fer H2L2H3- GGSGGGSG-1GQ3- GGSGGGSGGGSGGG SGGGSG-FerTrimers on LS (30) JCB_13_ CP- 60-94, 192- APGG linker, C-term. 1400GSGGGSG_LS SØ + CAV + DS + 232 GCN4, inter- Thr, Strep, GCNLS 4 + LSDS + LS and H8 JCB_19_ CP- 60-94, 192- GSG linker, C-term. 1401GSGGSG_LS SØ + CAV + DS + 229 GCN4, inter- Thr, Strep, GCNLS 4 + LSDS + LS and H8 TZ_05_GGSGGG_ CP- LS 192-242, 60- Glycine N-Strep-H8-1402 LS SØ + DS + CAV + 97 linkers + LS Thr charge + LS TZ_08r_GGSGGG_CP- LS 192-242, 60- Glycine N-Strep-H8- 1403 LS SØ + DS + CAV + 97linkers + LS Thr glycan + LS TZ_09r_GGSGGG_ CP- LS 192-242, 60- GlycineN-Strep-H8- 1404 LS SØ + DS + CAV + 97 linkers + LS Thr glycan + LSTZ_15_GGG-LS CP-SØ + DS + LS LS 58-97, 192- Glycine N-Strep-H8- 1405 242linkers + LS Thr TZ_16_GGG_LS CP- LS 58-97, 192- Glycine N-Strep-H8-1406 SØ + DS + CAV + 242 linkers + LS Thr LS TZ_17_GGG_LS CP- LS58-97, 192- Glycine N-Strep-H8- 1407 SØ + DS + CAV + 242 linkers + LSThr LS TZ_19_GGG_LS CP- LS 58-97, 192- Glycine N-Strep-H8- 1408SØ + DS + CAV + 242 linkers + LS Thr charge + glycan + LS TZ_20_GGG_LSCP- LS 58-97, 192- Glycine N-Strep-H8- 1409 SØ + DS + CAV + 242linkers + LS Thr charge + glycan + LS MS_03_ D3 + N-term. LS51-103, 139- Glycine N-Strep-H8- 1410 GGGSSGSGGGSSGG CCMPTD + LS 307linkers + Thr GSSGGGS_LS CCMPTD + LS MS_05_ D3 + N-term. LS 51-103, 146-Glycine N-Strep-H8- 1411 GGGSSGSGGGSSGG CCMPTD + LS 307 linkers + ThrGSSGGGS_LS CCMPTD + LS MS_07_ CP-D3, C- LS 51-103, 146- GlycineN-Strep-H8- 1412 GSGGGSSGSGG term. MTQ- 307 linkers + Thr GSSGGGSSGGGS_CC + LS CCMPTD + LS LS MS_08 CP-D3, C- LS 51-103, 146- GlycineN-Strep-H8- 1413 GGGSSGSGGGS term. MTQ- 307 linkers + Thr SGGGSSGGGS_CC + LS CCMPTD + LS LS MS_09_ CP-D3, C- LS 51-103, 139 GlycineN-Strep-H8- 1414 GGGSSGSGGGSSGG term. MTQ- 307 linkers + ThrombinGSSGGGS_ CC + LS CCMPTD + LS LS RSVF (+) THS_ CP D3 + EH +  LS 146-306-Glycine N-Strep-H8- 1415 s_to_foldon_ DS-Cav1 ggsgg (Seq_1448)-linkers, LS HRV3C gagggsggsggsg 50- gg_ls 105 + Fd RSVF (+) CP D3 + EH +  LS 146-306- Glycine N-Strep-H8- 1416 THS_s_to_  DS-Cav1ggsgg (Seq_1448)- linkers, LS HRV3C foldon A102C- 50- A241C_gagg105 + Fd gsggsggsggg_ls RSVF (+) CP D3 + EH +  LS 146-306- |GlycineN-Strep-H8- 1417 THS_s_to_hp12 DS-Cav1 ggsgg (Seq_1448)- linkers, LSHRV3C _foldon_ 50- gagggsggsggs 105 + Fd ggg_ls RSVF (+)  CP D3 + EH + LS 146-306- Glycine N-Strep-H8- 1418 THS_s_to_hp12 DS-Cav1 + Fdggsgg (Seq_1448)- linkers + T4 HRV3C foldon A102C- 50-105- Fd + LSA241C_gagggs ggsggsg ggsggsggg_ls (Seq_1445)- Fd RSVF (+) CP D3 + EH + LS 146-306- Glycine N-Strep-H8- 1419 THS_s_to_hp2 DS-Cav1ggsgg (Seq_1448)- linkers, LS HRV3C foldon_ 50- gagggsggsggsg 105 + Fdgg_ls RSVF (+) CP D3 + EH +  LS 146-306- Glycine N-Strep-H8- 1420THS_s_to_hp2 DS-Cav1 + Fd ggsgg (Seq_1448)- linkers + T4 HRV3Cfoldon A102C- 50-105- Fd + LS A241C_ ggsggsg gagggsggsggs (Seq_1445)-ggg_ls Fd RSVF (+) CP D3 + EH +  LS 146-306- Glycine N-Strep-H8- 1421THS_s_to_hp2 DS-Cav1 + Fd ggsgg (Seq_1448)- linkers + T4 HRV3Cfoldon_ds_ 50-105- Fd + LS gagggsggsg ggsggsg gsggg_ls (Seq_1445)- FdRSVF (+) CP D3 + EH +  LS 146-306- Glycine N-Strep-H8- 1422 THS_s_to_hp2DS-Cav1 + Fd ggsgg (Seq_1448)- linkers + T4 HRV3C foldon_ds 50-105-Fd + LS A102C-A241C_ ggsggsg gagggsggsggsgg (Seq_1445)- g_ls Fd RSVF (+)CP D3 + EH +  LS 146-306- Glycine N-Strep-H8- 1423 THS_s_to_hp2DS-Cav1 + Fd ggsgg (Seq_1448)- linkers + T4 HRV3C foldon_I221F_ 50-105-Fd + LS gagggsggsggsg ggsggsg gg_ls (Seq_1445)- Fd RSVF (+)CP D3 + EH +  LS 146-306- Glycine N-Strep-H8- 1424 THS_s_to_hp2DS-Cav1 + Fd ggsgg (Seq_1448)- linkers, LS HRV3C foldon_I221F 50-A102C-A241C_ 105 + Fd gagggsggsggsgg g_ls C-Trimer 1GQ3- CP-SØ + C-term.LS Glycine N-Leader- 1425 LS_60 mer: ATCase + LS linkers + E Strep-leader-Strep- coli ATCase HISx6-Thr HISx6-Thr- (1GQ3) + LSL1H1-K1-H2L2H3- GGSGGGSG-1GQ3- GGSGGGSGGGSGG GSG-LS C-Trimer 1GQ3-CP-SØ + C-term. LS Glycine N-Leader- 1426 LS_60 mer: ATCase + LSlinkers + E Strep- leader-Strep- coli ATCase HISx6-Thr HISx6-Thr-(1GQ3) + LS L1H1-K1-H2L2H3- GGSGGGSG-1GQ3- GGSGGGSGGGSGGG SGGGSG-LSC-Trimer 1GQ3- CP-SØ + C-term. LS Glycine C-Leader- 1427 LS_60 mer:ATCase + LS linkers + E Thr-H6- leader-L1H1- coli ATCase StrepK1-H2L2H3- (1GQ3) + LS GGSGGGSG-1GQ3- GGSGGGSGGGSGG GSG-LS-Thr-HISx6-Strep C-Trimer 1GQ3- CP-SØ + C-term. LS Glycine Strep 1428LS_60 mer: ATCase + LS linkers + E C-Leader- leader-L1H1- coli ATCaseThr-H6- K1-H2L2H3- (1GQ3) + LS GGSGGGSG1GQ3- GGSGGGSGGGSGGG SGGGSG-LS-Thr-HISx6-Strep

Example 15 Immunogenicity of Prefusion Stabilized F Protein

A series of assays (in addition to those provided above) were performedto illustrate the immunogenicity of the recombinant RSV F proteinsprovided herein that are stabilized in a prefusion conformation. Theresults show that the provided recombinant RSV F proteins stabilized ina prefusion conformation can be used to induce an immune response inmultiple animal models, and further that induction of this immuneresponse protects against future viral challenge.

Unless indicated otherwise, in FIGS. 73-84 , and in this example,reference is made to the following recombinant RSV F proteins:

-   -   DS (Subtype A)=RSV A2 F(+)FdTHS S155C, S290C (SEQ ID NO: 185)    -   DS (Subtype B)=RSV B18537 F(+)FdTHS S155C, S290C (SEQ ID NO:        1479)    -   DS-Cav1 (Subtype A)=RSV A2 F(+)FdTHS S155C, S290C, S190F, V207L        (SEQ ID NO: 371)    -   DS-Cav1 (Subtype B)=RSV B18537 F(+)FdTHS S155C, S290C, S190F,        V207L (SEQ ID NO: 372)    -   Postfusion F (Subtype A)=RSV A2 F(+) dFPTHS

FIG. 73 illustrates that, using Ribi as adjuvant, a single chain versionof DS-Cav1 presented in the context of a ferritin nanoparticle given IMelicits a small but detectable neutralizing antibody response after 2weeks in rhesus macaques after a single dose. Based on these small butdetectable responses after one dose it is expected that after boostingwith a second dose a significant neutralizing antibody response will beinduced. This would be consistent with the immunogenicity of 2 mcg ofcleaved DS stabilized prefusion F trimer presented on a ferritinnanoparticle formulated with Ribi after 2 doses in mice, discussedbelow.

As illustrated in FIG. 74 , mice (CB6F1/J) an immune response to the DSversion of stabilized prefusion is induced in mice immunized with 20 mcgof DS F in 50 mcg of poly ICLC on weeks 0 and 3. Neutralizing activitywas maintained at a high level in DS immunized mice for more than 12weeks.

As illustrated in FIG. 75 , immunization with DS (Subtype A)=RSV A2F(+)FdTHS S155C, S290C (SEQ ID NO: 185) can prevent RSV infection in ananimal model. Mice were immunized IM with the DS version of thestabilized F protein (SEQ ID NO: 185) at week 0 and week 3. Mice werechallenged intranasally with 10e7 pfu of homologous RSV A2 virus on week19, four months after the last vaccination. On day 5 lungs and noseswere removed to measure virus load in tissue. The results show that miceimmunized with the DS version of prefusion F had no detectable virus inlung or nose.

Further, the mice administered DS (Subtype A)=RSV A2 F(+)FdTHS S155C,S290C (SEQ ID NO: 185) did not undergo a Type 2 cytokine response to theimmunogen (FIG. 76 ). Cytokine content was measured in lung and nosesupernatants on day 5 following initial immunization with control (PBS),wild-type RSV (RSV), formalin inactivated RSV (FIRSV), DS (SEQ ID NO:185; “pre-fusion F), or a stabilized post fusion F construct(post-fusion F). Mice undergoing primary infection had significantlevels of IFN-gamma and MIP-1alpha as expected. FI-RSV immunized micehad significant levels of type 2 cytokines (IL-4, IL-5, and IL-13) andcytokines associated with epithelial damage (IL-6) typical of responsesassociated with vaccine-enhanced disease. Mice immunized with prefusionF (DS) had a modest level of IFN-gamma and IL-10 associated with aneffective and regulated response and no illness or weight loss.

The neutralization activity of serum from non-human primate modelsimmunized with the recombinant RSV F DSCav1 protein (SEQ ID NO: 371) wasassayed over the course of a three-dose immunization (FIG. 77 ). Rhesusmacaques, 4 per group, were immunized twice at 0 and 4 weeks with 50 mcgIM with either DS-Cav1 prefusion F (SEQ ID NO: 371) or postfusion Fbased on subtype A sequence and formulated with poly ICLC. On week 26,both groups were boosted with 50 mcg IM of DS-Cav1 prefusion Fformulated with poly ICLC. After 2 doses of DS-Cav1, significantneutralizing activity is induced and sustained above the protectivethreshold for more than 5 months. Postfusion F was immunogenic andinduced detectable neutralizing activity after 2 doses, but was onlytransiently above the protective threshold. Boosting the postfusion Fgroup with a 3^(rd) dose of DS-Cav1 stabilized prefusion F resulted in arise in neutralizing activity above that achieved after the 2^(nd) dose.After the 3^(rd) dose neutralizing activity against the homologoussubtype A was stably maintained for over 10 weeks as highlighted in thered boxed areas.

To demonstrate that the DSCav1 construct can be formulated with Alum,purified DSCav1 (SEQ ID NO: 371) was mixed with Alum hydroxide gel orAlum phosphate gel at various ratios. BALB/c mice were immunized IM with10 mcg of DS-Cav1 version of stabilize prefusion F formulated with alum(either aluminum hydroxide gel or aluminum phosphate gel) at 0 and 3weeks. The protein:alum wt:wt ratios were varied between 1:1 and 1:10.All formulations were immunogenic (FIG. 78 ). In addition, use of Alumas an adjuvant for DSCav1 immunization was demonstrated in a non-humanprimate model (FIG. 79 ). Rhesus macaques were immunized at week 0, 4,and 26 with purified DS protein (SEQ ID NO: 185). The week 0 and 4injections were comprised of the DS version of stabilized RSV prefusionF (50 mcg) formulated in poly ICLC. The week 26 boost was 50 mcg of theDS prefusion stabilized F formulated in aluminum phosphate gel.Therefore alum is an effective adjuvant for the stabilized prefusion Fin NHP.

To show that another immunization protocol is effective for inducing aneffective immune response with DSCav1, mice were immunized with agene-based vector expressing DSCav1, and the resulting immune responseto RSV F was evaluated (FIG. 80 ). CB6F1/J mice were immunized with arecombinant adenovirus serotype 5 vector expressing the wild-typeversion of F at 0 and 3 weeks or were immunized at week 0 with rAd5expressing the DS-Cav1 version of preF membrane anchored (non-secreted)and boosted with 10 mcg of DS-Cav1 formulated in alum at week 3.rAd5-preF primed mice boosted with DS-Cav1 in alum produced as muchneutralizing antibody as mice given two doses of protein only indicatingthat prefusion F delivered by a gene-based vector is immunogenic and canprime for a subsequent protein boost.

Additionally, the DSCav1 protein was effective for boosting an immuneresponse to wild-type (WT) RSV F (FIG. 81 ). Non-human primates primedwith recombinant adenovirus vectors expressing WT versions of RSV F(subtype A) more than 2 years before boost, were boosted with a single50 mcg dose of DS-Cav1 subtype A or subtype B formulated in alum. Twoweeks after boosting neutralizing activity was significantly increasedby both subtype A and B DS-Cav1 proteins (FIGS. 81-82 ).

To demonstrate the cross-subtype effectiveness of the DS (S155C, S290C)version of stabilized F, CB6F1/J mice were immunized IM with 10 mcg ofDS formulated in Ribi at week 0 and week 3 (FIG. 83 ). Neutralizingantibody was induced by both A (SEQ ID NO: 185) and B (SEQ ID NO: 1479)subtype proteins against both subtype A and B viruses. The groupreceiving both A and B received a total of 20 mcg of protein.

FIG. 84 illustrates that altering the glycosylation of the RSV F proteinreduces its immunogenicity. BALB/c mice were immunized with 10 mcg ofthe DS version of stabilized prefusion F formulated in poly IC at weeks0 and 3. The F constructs were treated with glycosidases or mutantversions were made to remove glycosylation sites at N27 and N70. The Fprotein could not be produced if the N500 glycosylation was mutatedsuggesting that glycosylation at that site is required for expression.Neutralizing activity was detected at week 5 (solid bars) and week 7(hatched bars) in mice immunized by any of the glycosylation variants ofF. However, altering glycosylation appeared to reduce immunogenicitycompared to the original DS version of stabilized prefusion F.****=P<0.0001.

It will be apparent that the precise details of the methods orcompositions described may be varied or modified without departing fromthe spirit of the described embodiments. We claim all such modificationsand variations that fall within the scope and spirit of the claimsbelow.

We claim:
 1. An isolated immunogen, comprising a recombinant RSV Fprotein or an extracellular domain thereof comprising a S190Isubstitution that stabilizes the recombinant RSV F protein or anextracellular domain thereof in a prefusion conformation, wherein theamino acid positions of the RSV F protein are according to a referenceRSV F protein sequence set forth as SEQ ID NO:
 124. 2. The immunogen ofclaim 1, wherein the recombinant RSV F protein or extracellular domainthereof comprises an F2 polypeptide and an F1 polypeptide comprisingamino acid sequences at least 90% identity to residues 26-109 and137-513, respectively, or 26-103 and 145-513, respectively, of SEQ IDNO:
 910. 3. The immunogen of claim 1, wherein the immunogen specificallybinds to a D25 or a AM22 prefusion-specific antibody.
 4. The immunogenof claim 1, wherein the RSV F protein or extracellular domain thereof isa RSV A, B, or bovine RSV F protein or extracellular domain thereofcomprising the amino acid substitution.
 5. The immunogen of claim 1,wherein the recombinant RSV F protein or extracellular domain thereof isa single chain protein comprising F₂ and F₁ polypeptides linked by aheterologous peptide linker, or directly linked.
 6. The immunogen ofclaim 5, wherein position 105 of the F₂ polypeptide is linked toposition 145 of the F₁ polypeptide by a Gly-Ser linker; or position 103of the F₂ polypeptide is directly linked to position 145 of the F₁polypeptide.
 7. The immunogen of claim 1, comprising a multimer of therecombinant RSV F protein or extracellular domain thereof.
 8. Theimmunogen of claim 1, wherein the recombinant RSV F protein orextracellular domain thereof is linked to a trimerization domain.
 9. Theimmunogen of claim 8, wherein the trimerization domain is a Foldondomain.
 10. The immunogen of claim 1, wherein a C-terminal residue of anF₁ polypeptide of the recombinant RSV F protein or extracellular domainthereof is linked to a foldon trimerization domain.
 11. The immunogen ofclaim 8, comprising the extracellular domain of the RSV F protein linkedto the trimerization domain, and an amino acid sequence at least 90%identical to residues 26-109 and 137-544 or 26-103 and 145-544 of SEQ IDNO:
 910. 12. The immunogen of claim 1, wherein a C-terminal residue ofan F₁ polypeptide of the recombinant RSV F protein or extracellulardomain thereof is linked to a transmembrane domain.
 13. A virus-likeparticle comprising the immunogen of claim
 1. 14. A protein nanoparticlecomprising the immunogen of claim
 1. 15. The protein nanoparticle ofclaim 14, wherein the protein nanoparticle is a ferritin nanoparticle,an encapsulin nanoparticle, a Sulfur Oxygenase Reductase (SOR)nanoparticle, a lumazine synthase nanoparticle or a pyruvatedehydrogenase nanoparticle.
 16. The immunogen of claim 1, wherein a Fabof monoclonal antibody D25 or AM22 specifically binds to the immunogenwith a K_(d) of 1 μM or less.
 17. A nucleic acid molecule encoding theimmunogen of claim
 1. 18. The nucleic acid molecule of claim 17, whereinthe nucleic acid molecule encodes a precursor protein of the immunogenor protein nanoparticle.
 19. The nucleic acid molecule of claim 17,wherein the nucleic acid molecule is an RNA molecule.
 20. A vectorcomprising the nucleic acid molecule of claim
 17. 21. The vector ofclaim 20, wherein the vector is a viral vector.
 22. An isolated hostcell comprising the vector of claim
 20. 23. An immunogenic compositioncomprising an effective amount of the immunogen of claim 1 and apharmaceutically acceptable carrier.
 24. A method for generating animmune response to RSV F protein in a subject, comprising administeringan effective amount of the immunogen of claim 1 to the subject togenerate the immune response.
 25. An isolated immunogen, comprising: anextracellular domain of an RSV F protein fused to a foldon trimerizationdomain, wherein: the extracellular domain of the RSV F protein comprisesa S190I substitution; the extracellular domain of the RSV F proteinfused to the foldon trimerization domain comprises an amino acidsequence at least 90% identical to residues 26-109 and 137-513,respectively, or 26-103 and 145-513, respectively, of SEQ ID NO: 910;and wherein the amino acid positions are according to a reference RSV Fprotein sequence set forth as SEQ ID NO: 124.